My husband refinished the hardwood floor in the bedroom of our first house. We had to rent two sanders--one to do the main parts of the floor and the other to do the edges. It was about $100 for the rental of both, plus the polyurethane or whatever you finish it with. It was really hard work. He called me at work a few minutes into it and said there was no way he could do it. But we'd already spent the $100 so he kept going. He ended up doing a really beautiful job, but it was not easy.
We have hardwood in our current house in the front hall and kitchen. It's getting pretty beat up (especially where the kitchen chairs are), but I'm hoping that someday we can hire someone to do this job, although it might be a while.