Personally, I don't like putting any bettas in community tanks. They are slower than most fish, so they can get nipped, and they can get very terrortial and aggressive, I've seen many a tetra missing an eye after someone added a betta to the tank.
Honestly, a single betta in a 5 gallon, slow-filtered, heated tank with tall plants to rest on is ideal. He has his own spot and no competition for food or constant nipping of other fishies.