Guppies, mollies, swordtails, and platys. They all give live birth. I started out with about ten. 2 or 3 of each kind. I now have two ponds and one aquarium full of those community fish.
It's really easy to breed them. just put them in a tank by themselves, and sooner or later they'll get pregnant. When they do, separate the mother from the rest of the fish. You'll know when she's pregnant. Her belly will get really big. It's hard to miss. Put her in another tank and fill it with plants. This way, when she gives birth, the fries have hiding places. I do not recommend breeder nets or separaters as the fries often do not stay where they're supposed to be and end up being gobbled up by other fish or the mother.
Hope that all helps! Good luck!