Breeding Betta Splendens a.k.a. Siamese Fighting Fish a.k.a. Cupang might profit you economically. You don't need a lot of space to breed Betta, and actually there's no special requirement. Many people like to see and to have Betta because of its beautiful color and shape. As its name tells, if male Betta meet another male Betta, they will fight against each other until one of them lose, or die. This is one of the reasons why people like Betta Splendens. The price usually depends on the beautiness of the color and shape of its body and fins. In my country in Indonesia, the price ranged between $5-10 each, and up to $100 for Betta that's ready for competition. The cheapest one (and most likely the one that's mediocre) is $1 or so.

Anyone can breed Betta Splendens. You can even use buckets, small aquarium, or even cans. They will live normally in small room, even inside a bottle of beer (drink up the liquid first, then fill the bottle up with pure water). But please don't breed Betta Splendens while you're drunk. ;)