Valerie, I think it's a good idea to start out with 2 hives. You can better observe how they are doing and if one is thriving and the other not, you can check the slower one. In some situations, you may even want to give the slower hive a frame of brood from the strong hive to help them out. I don't, as a rule, tinker much with them but it's nice to have the option.
And if at all possible, get swarms that are
local rather than ordering
bees shipped in from far away places. Local
bees understand our weather and cycles and are more tuned to them.
One thing to be aware of -- have interchangeable equipment so a frame from one hive fits the other. Oh, I can't tell you how many times I've wished someone had made me understand that! I have maybe TWO hives that I can interchange equipment on, that's all. Everything else is different. Even my warres and top bars are all different types and sizes.
Pick one and stick with it for a long time. Experiments can come later. Much later.
warmly
Jacqueline