When we got our danios they were on sale at Petsmart for $0.69. At that price, it is a lot cheaper to buy them than to breed them. If you want to breed a few fish for the fun of it, or to sell a few, livebearers (guppies, mollies, platies, swordtails and endlers) are probably a lot easier. We got our swordtails on sale at Petco for $1.99. I still find the concept of live animals "on sale" a little strange.