If I get a rabbit, Do I *HAVE* to get two of them? Plus more questions!?

I really want a rabbit, but I will buy my rabbit at a place where the rabbits are $20 or $25 for 1. I really can't afford to pay $50 for two rabbits plus all the other things to go with it. Do I really need to buy 2 rabbits? Is it OKAY to keep a rabbit in a cage in my garage which is cool in the summer and some what warm in the winter? I have a wiener dog that goes nuts when we get small animals like rabbits. If I buy a rabbit, Does it need gr or do I have to keep it in an outside hutch?