You have to be careful with those floor sanders. They can really get away from you. I've seen footage of people loosing control when trying to use them.
If you decide to go with vinyl sheet or linoleum, you can check out surplus places or Habitat for Humanity ReStore to find supplies for less expense. The latter doesn't always have what you're seeking, but its worth a look since they tend to have very good prices on things. I found some doorknobs that were normally $30 for $2 there. They sometimes have extra flooring and such. (The ReStore sells stuff that was donated to them from when houses were demolished/renovated or when people had extra stuff leftover after a renovation). If it wasn't such a large area, I'd say you could look for remnants at some stores because those are usually less expensive.