I will assume that you have already heard about the Roman empire or have read other sources as to what slavery is. For those who do need a definition slavery is the ownership and/or to force labour onto someone without them being paid. You might be asking why the picture of the Sphinx and pyramids? Well simply because I found a book named "The Romans" by Anthony Kamm which gives that date leading me to want to show what slaves have accomplished over a time. If I am not mistaken the Pyramid is Keops recognizable by what is left of the smoothened surface. (sorry to digress).
At the beginning of the empire slavery was not so current but later on as more and more provinces were occupied enemies were taken and sold as slaves. These ranged from Greeks to some barbarians. These barbarians were used as labour in third empire. Greeks on the other hand were educated and so were used to teach the Roman people about things. From this you can see how important the slave was at the time.
Slaves were a surplus to such an extent that even slaves could own slaves of their own. The difference was that the qualities of the slaves were different. For example a rich man could buy a slave which would be able to rule his home and educate his children. The slave could then also own a slave but this time for it's own use. This become common practice after the third century BC (Source: "Everyday life in Ancient Rome" by F.R. Cowell. It is located in chapter IV on slavery).
This was due to the fact that the Romans had a huge army consolidating the Roman empire and gaining submission from the defeated countries. These people were then taken as slaves and so this is what caused the great influx.
The cost of slaves could vary according to the qualifications of the slave. If a slave was weak and could not do much work then he could fetch very little or if it was a very capable slave which could do a lot then the cost was high. Some people bought young untrained slaves which they trained to be able to sell the slaves at a profit. Other slaves could be bought from a price of 500 denarii to 875,000. This is a demonstration of the difference in wealth between slave owners (Form slaves to rich masters). Slaves could buy their own slaves and sell them to their owners or keep them to help them in the labour. Tariffs for slaves could be the following: a nurse and two children could be sold for 1,800 denarii. The Romans admired beauty such that a pretty girl could reach from 2000 to 6000 denarii. A music girl cost 4000 denarii. Later on in the empire people were prepared to spend vast amounts on just a slave boy.
On farms the slaves had to take care of the fields and also the houses of the owners. Some farms were family farms and so didn't have many slaves as they could do it themselves. Rich farmers on the other hand were able to get a lot of slaves which were qualified to take care of other problems The rich farmer was a manager which had slaves to be the workers. Sometimes qualified slaves were used as administrators since they had previous experience or the owner thought they could be trusted.
Other slaves were government owned. Some ended up becoming gladiators while others had to do road works and other jobs. As I have mentioned before the methods of construction I will assume that you have read that too. Slaves had to work in the warm Mediterranean climate which at the time was warmer. They had to carry the blocks of marble and other materials themselves on carts and other transport methods.
Slaves could earn there freedom in a number of ways depending on there role as a slave. Some slaves could get freedom relatively easily compared to others. For example a qualified slave such as a Greek serving in a rich man's house was treated with respect and was spared manual labour.
Some other slaves on the other hand were forced to do a lot of work on farms and in provincial work. They might have been mistreated and beaten etc. They could get beaten and it would not be considered abusive for the owner to do so. In farm work the farmer was said to have free tools with which to work the land which are the following: The chariot for transport, the inarticulate such as the oxen and those with voice such as the slaves. This tells us a little about the situation which the slaves were in.
Combatant slaves such as gladiators or chariot racers had to win their freedom in a much harsher way. The gladiator had to confront vicious animals such as lions and other animals in an arena so that the Roman citizens could entertain themselves. Gladiators were in a difficult position to get out of as they had to fight valiantly and avoid to be killed and after a number of years without been killed they earned the status of freedman.
Chariot racers had a very dangerous job as they had to race horses on chariots which were frail and so disintegrated easily. They had to tie the reigns of the horses around there chest so that they did did were attached to the horses. In case of a crash they had to cut themselves loose fast or they would be dragged along the floor and so die. They therefore carried a knife on them in case of this eventuality. In both gladiator fights and chariot races the slaves could earn a lot of money from bets on them. Slaves also had the possibility to buy their freedom from their masters.
Conclusively people were not born into slavery but instead were forced into it for a number of years after which they could be freedmen (liberti in Latin) with land and slaves of their own.
If you know any other sites related to either history or Slavery from the time please tell me about them so that I can view and add them if they are good