Here in Brazil, I have seen many different methods of farming tilapia so when someone tells you there is only one way, they are wrong.
The things which are necessary are water (of course), air (either natural or generated), and food.
The health of your fish and the profitability of your business will be determined by those 3 factors and the quality of each of these things.
One couple in the village where we live, began their business in a roundabout fashion. They have a lovely home and small grounds. What they do have is a small stream which flows from the dunes down towards the sea. They dug out an area, about 15 feet across, laid cement and presto they had a lake/pond. The water was allowed to continue flow through of course. Into this they put their tilapia. In the center of the pond they had a aerator for the fish. They had a beautiful wooden deck surrounding the pool of water so you could see the fish. Their grounds also have picnic tables, a swimming pool and grassy areas.
They had started this as a 'fish and pay'. People, families in the main, would come and fish for fun, and when they caught a tilapia they would pay. I still think this is a great idea although in this area, it wasn't as successful as it would be in other areas.
This couple also built a fully tiled kitchen prep area within their grounds. In here they prepared fish balls and other small appetizers which are frozen and then sold to the local stores.
The advantage of this set up is everything is compact and easily managed. The running water is free from the dunes behind their house. The disadvantages are they are reliant on this water. If this dried up they would have to dig a well and pump it themselves. This isn't a big cost here, though. Because of the fish density and the time needed to grow their fish to 2 kilos, there is the potential for a disease which could wipe out their entire stock. There is also only one pay out which needs to last until the next harvest.
Another local tilapia farm has a completely different method. At this farm they had several shallow lakes, about 1.5 meters deep, spread across their land. In the center of each lake they had fixed aeration. They also had a small amount of water which flowed from one lake to another so they had a change of water. This was run by a couple of workers who lived on the grounds and the owner lived in the city and visited occasionally . They raised their fish to approx 450-500grams only. Then the lake was netted and the fish were sold. The reason for this is tilapia will begin to breed which causes problems to the profitability of your farm.
Although the fish are relatively small when sold, they go to the local shops and to restaurants which make them into a casserole when the fish is cut up as opposed to serving someone a whole filet.
At this farm we noticed they had netting stretched across the top. This was to discourage egrets, herons, and cormorants from eating the fish. Once their lakes were netted, the lake was drained and cleaned. These lakes are lined with compacted clay and once the water has drained or evaporated away the fish shit is scraped off and removed. Theirs is a year round business as they always have fish of different ages so they can provide a continuous supply.
The advantage of this set up is there is a continuous supply and a continuing payout. The disadvantages are: The initial costs include the digging of the lakes and investment in the equipment for aeration, and considerable pumps to constantly move water around. This coupled with the employment of at least two people.
The next farm was some distance away and it is where we bought our used fish cages which we used for our second year of fish farming. This gentleman worked his business primarily on his own. He didn't own a body of water he merely put his fish in cages in a river. To feed these he used a row boat which took about 10 minutes to row out to the cages as they were secured in the center of this wide river.
This way of tilapia farming has advantages and disadvantages. The advantage is the initial investment was small. All he had to buy was his cages, fish and food. And a row boat of course.
The disadvantage is the potential of theft. A person wouldn't know if fish had been taken until either no fish came to the surface to feed or at harvest time when you realize your numbers are way down.
This man knew many of the families who lived near this body of water and they all watched out for each other. We asked him if he was concerned about this and he had made it clear to people of the serious consequences of stealing from him. Here in Brazil people take action themselves and don't always rely on the police and the judicial system.