Michael Allen Lee: grammar and meaning notes
1 he had been convicted
If someone is 'convicted' of a 'crime,' this means that they have been found 'guilty' of that crime in a 'court' and 'sentenced' by a 'judge' to some kind of 'punishment.' The verb 'convict' is only used in a 'legal CONTEXT.' The word 'convict' is also used as a NOUN to refer to a person who has been convicted of a crime and sent to prison as a punishment. There is another noun form, 'conviction,' which is used to refer to what happens when someone is convicted of a crime. For example: "Harry's lawyers were surprised by his conviction." (There is also an unconnected but important use of the word 'conviction' to refer to 'what a person believes,' as in "Jill refused to discuss her religious convictions with Jack.")
This is the NOUN form of the verb 'enslave,' which means 'to make into a slave' or 'put into slavery.' The SUFFIX 'ment' is often used to make a noun into a VERB. For example, 'development' is the noun form of the verb 'develop,' and 'government' is the noun form of the verb 'govern.' The verb 'enslave' is made from the noun 'slave' by using the PREFIX 'en.' The prefix 'en' is often used in English to make verbs that have the meaning of 'putting into.' For example: 'encase' means 'put into a 'case' (a small box); 'encode' means 'put into code'; 'enclose' means 'put into a closed area'; 'encourage' means 'put into a courageous condition'; and 'endanger' means 'put into danger.'
3 'this happened in Fort Pierce'
'This' is a PRONOUN here but it does not 'replace' a single noun as pronouns basically do. It refers to the whole situation described in the previous sentence Michael's being convicted of enslavement and sent to jail. It is much better to use 'this' here than it would be to use 'it.' Generally 'it' is used only when it can be seen as replacing a SPECIFIC noun, noun phrase or noun clause. (One way of putting this would be to say that 'this' can be used to make a VAGUE REFERENCE but 'it' cannot be used in this way.) (See  below.)
4 prosperous farms
'Prosperous' has approximately the same meaning as 'rich.' It is not quite right, however, to speak of a 'rich farm' or a 'rich business.' In general, only people can be described as 'rich.' Both 'prosperous' and 'rich' can be used to describe people who have a lot of mopney , but 'prosperous' has CONNOTATIONS that 'rich' does not have. To say that a person is prosperous is not only to say they have a lot of money, it is also to say that they are that they are making a lot of money, and they are propbably going to make more in the future in other words, that they are 'financially healthy.' (The noun form of 'prosperous' is 'prosperity.')
5 'was working...was hiring
These verbs are in the PAST PROGRESSIVE because they are being used to 'set the CONTEXT' of the story. The past progressive is most often used to describe a situation in which one large, 'enclosing' situation 'contains' a smaller, 'enclosed' event, as in "Jack arrived while Jill was washing the dishes." Its use here is similar even though no enclosed event is actually mentioned. The IMPLICIT enclosed event is 'the beginning of the story.' (The story could have begun: "When the story began ,Michael was working...')
6 labour boss
Here, 'labour' refers COLLECTIVELY to all the workers (the 'labourers') who were picking fruit on the farms. working. Michael was a 'labour boss' because he was the boss of those men.
7 'migrant workers
'Migrant' is the noun form of the verb 'migrate' which is used to describe the temporary movement of large numbers of people or animals from one place to another. In the phrase, 'migrant worker,' 'migrant' is used as a NOUN MODIFIER. The most common use of the verb, 'migrate' is to describe the annual (yearly) movements of birds from the north to south and back again. It would be unusual but correct to speak of farm workers migrating from the US to Mexico and back again. The adjective form of 'migrate' is 'migratory'; birds that migrate are 'migratory' birds; it would also be correct to speak of 'migratory workers.' The noun form of 'migrate is 'migration.' 'Migrate' is also connected with the verbs 'immigrate' and 'emigrate,' words that REFER to permanent movements of people from one country or another. (All these words come originally from the LATIN, 'migrare,' which means 'to move from one house to another.')
8 shelters for homeless men
The basic meaning of 'shelter' is 'a place where people are protected from the weather.' A shelter is usually a building of some kind even if it is only a very poor one. But it does not have to be a building: trees provide shelter from the sun, for example. The word is appropriate for a building for homeless people because without a shelter, they have no protection from the weather. 'Shelter' is used, METAPHORICALLY, in the phrase 'tax shelter' a place to invest money so that it will not be taxed. And it is also used as an ordinary verb and as a BUILT-IN OBJECT in the CLAUSAL VERB, 'take shelter.' (For example: "During the storm, Dick and Jane took shelter under a tree.")
9 a run-down house
A run-down house is a house that is in poor condition because it has not been properly taken care of. It is a COMPOUND ADJECTIVE based on the PHRASAL VERB 'run down.' The adjective 'run-down' can also be used to describe a person who is in poor physical condition because they are sick or very tired. Although the adjective is based on the verb it has a 'separate' meaning; it would not be normal to say, for example that a house ran down; it would be better to say that it 'became run-down' or 'got run-down.' (The verb 'run down' is common and has several meanings: to hit someone with a car; to criticize someone; and to chase someone and catch them.) (And 'run-down' is also used as a noun to mean 'a summary,' as in "Tom gave Harry a quick run-down of what had happened in his meeting with Sarah.")
10 the money was deducted
'Deducted' is the PAST PARTICIPLE of 'deduct' which means 'subtract' or 'take off' a certain amount. The noun form is 'deduction.' Both the noun and the verb are used very often in connection with paychecks and income tax. In some countries, income tax and pension contributions are deducted from paychecks and in some countries people paying income tax are allowed to make deductions because they have children or because of their medical expenses. ('Deduction' is also the noun form of the verb 'deduce,' which means 'come to a conclusion on the basis of evidence,' as for example, in "By observing their behaviour Harry deduced that Dick and Jane had been fighting," or "By a series of careful deductions Jack came to the conclusion that Jill didn't love him anymore."
11 drinkable water
'Drinkable water' is water than can be drunk withough endangering health. The SUFFIX 'able' is often added to a verb in order to make an adjective. Such an adjective indicates that the action described by the verb is possible. Other adjectives formed in the same way are 'washable,' readable,' and 'reliable.'
11a 'they were taken into a van'
A 'van' is a small, covered truck, usually used for deliveries and carrying light loads. A small van is similar in size to an SUV (sports-utility vehicle) but the back part has no windows.
11b 'the van was over-crowded'
'Crowded' and 'over-crowded' mean approximately the same thing. To say something is, 'over-crowded' however, is more negative than simply to say that it is 'crowded.' If someone says a restaurant is 'over-crowded,' for example, they mean that because there are so many people there, the restaurant is not a pleasant place to be: it is too hot, or too noisy, or there is nowhere to sit. If someone just says that a restaurant is 'crowded' they only mean that there are a lot of people there; they may be happy or unhappy about this but we can't tell how they feel from what they say. (One way of expressing this would be to say that 'over-crowded' has a negative CONNOTATION but that 'crowded' is 'neutral.')
12 they did have water
The AUXILIARY VERB 'do' is used here to EMPHASIZE the CONTRAST between the things they did have and the things they did not have.
12a they had no cups to drink it from
To drink it from is a to-infinitive adjective clause a type of non-finite clause. It can be seen as a short form of the finite adjective clause from which to drink it. However, as is often the case when a to-infinitive adjective clause is used, it is preferable to the full finite clause. (In other words: it sounds better and more natural to native speakers.)
12b 'they pooled what they got'
The verb 'pool' is based as a METAPHOR on the noun 'pool.' A pool is a small area area of water for example a wide area of a stream or small river where the water is not running quickly, or a man-made area for swimming (a 'swimming pool'). The verb 'to pool [money]' is used to describe a situation in which several people contribute money and use the total amount to buy something; the amount of money collected is often referred to as 'a pool.' 'Pool' as a noun also refers to a game played on a flat table in which balls are hit with 'cues' (long sticks).
13 they had hot dogs
A hot dog is a narrow 'bun' (a small loaf of bread), cut open and with a special sort of sausage (called a 'frankfurter' or 'weiner') placed inside. It is eaten with the hands.
14 Michael's associates
A person's 'associates' are the people they do things with and, especially the people they work with. This word can also be used as a verb, for example in a sentence like, "Jill told Jack she didn't want to associate with Sarah and her friends." ('Associate' like the words 'social' and 'society' comes from the LATIN word 'socius,' meaning 'companion' or 'friend.' )
14a 'he got them to sign the checks'
This has the same meaning as the CAUSATIVE statement: "He had them sign the checks." Notice, however, that here the 'to'-infinitive is used, whereas in the causative the base form is used.
15 deposited them in his bank account
'Deposit' means 'to put something into something,' as in "Jill carefully deposited Jane's photograph in her desk drawer." In most CONTEXTS it is quite FORMAL and not common, but it is the ordinary, non-formal word to use when speaking of putting money into a bank account.
16 charged them for the sacks
The verb 'charge [someone] for [something]' means to ask that person to pay money for that thing.
To charge [someone] for [a crime]' is a DITRANSITIVE PREPOSITIONAL VERB. (Compare with 'charge [someone] with [a crime]' in  below.)
17 if they tried to leave, he would find them and punish them
This is a CONDITIONAL statement.. The best way to understand it is as a PRESENT, REAL CONDITIONAL that is written in the past because it is part of a NARRATIVE about the past. Michael's exact words would have been something like, "If you try to escape, I will find you and punish you."
18 'more than half of'
This phrase is a QUANTIFIER a structure that precedes a noun (or pronoun as in this case) and indicates 'amount' or 'number.' Other quantifiers are 'a lot of,' 'many,' 'some,' 'a small percentage of.' (Notice that the word 'than' here is not acting as a conjunction as it does in sentences like, "Jack earns more money than Jill does.)
19 that is what happened
'That' here is a PRONOUN but it refers, VAGUELY, not to a specific noun, but to what Michael told his workers. (See  above.)
20 he beat him
Here 'beat' means to hit someone repeatedly in order to hurt them or to make them feel pain. When this word is used to describe an attack on a person, it is IMPLIED that the person being beaten does not 'fight back.' (There is another important meaning for 'to beat someone' to play a game against them and win, as for example, "Sarah easily beat Harry at chess." When it is used in this way 'beat' is a DITRANSITIVE PREPOSITIONAL VERB, 'beat [someone] at [a game]')
21 Michael tried to keep George captive
The OBJECT of this SIMPLE SENTENCE is 'George' and 'captive' is an OBJECT COMPLEMENT.( 'Keep' is one of a quite small number of English verbs that 'take' an object complement.)
22 went to the police to make a complaint
'Make a complaint' is a CLAUSAL VERB with a BUILT-IN OBJECT. It is similar in meaning to the ordinary verb 'complain' but it is used when to describe an official complaint, for example, to the police, to the government, or to a store.
23 'started a lawsuit'
A 'lawsuit' is the procedure that takes place when someone is 'sued' in other words when Person A is taken to court by Person B because Person B believes Person A has harmed him or her in some way. (Lawsuits are a matter of 'civil' not criminal, law. If the person being sued loses a lawsuit, they will be forced to pay money to the person suing them, but they will not be sent to jail.) Often it is possible to describe this sort of situation either with the verb 'sue' or the noun 'lawsuit.' For example, "Sarah told Jack she hoped to avoid a lawsuit in connection with her divorce" is more or less the same as "Sarah told Jack she hoped her husband was not going to sue her in connection with their divorce." In the text, however, to say that George and the other workers 'started to sue' the company would be misleading because it would give the impression that after starting they decided not to continue.
24 'Michael was charged with enslavement'
When someone who has been 'arrested' by the police is charged with a crime, they are told by the police or a judge why they have been arrested and an official record is made of the 'charge.' Then the person who has been charged will be held in prison until their 'trial' or perhaps released 'on bail' until that time. '
To charge [someone] with [a crime]' is a DITRANSITIVE PREPOSITIONAL VERB. Notice that here the 'direct object' appears in the subject position because the verb phrase is in the PASSIVE VOICE. (There is another use of this verb in the last paragraph of the text.)
25 'they find it more 'efficient' to let...'
'Efficient' is put in quotation marks here to indicate that it is probably not really because of a concern for efficiency that the companies have labour bosses hire the workers for them. It is more likely that they do this because they don't want to be directly involved in the bad treatment of the workers. (When quotation marks are used in this way they are sometimes called 'scare quotes.')
26 'they had no idea/an idea (of)'
To say that someone has 'no idea' of something means that they know nothing of that fact or that subject. For example "Sarah has no idea that Jack dislikes her," or "Sarah had no idea what Jack meant when he asked her if she had the key." (The word 'of' is not used when the object of the verb is a 'that'-clause.) To say that someone 'has an idea' means they think something is true but they are not sure. For example, "Jane said, 'I have an idea that Jack dislikes Sara," means that she thinks Jack dislikes Sarah but she is not sure he does.