What would happen if you just cleaned them thoroughly?

The usual color was "natural", and the usual flooring was "whatever the budget could handle". I've seen maple, oak, cypress, teak, walnut, pine and hickory - all in the same neighborhood.

Very narrow, pale boards = maple? If so, staining it is difficult, and natural is lovely.

Can you post a closeup of the boards? And an overall shot of the floors?

If narrow probably floorboards are original. If light, I would guess maple. I would NOT stain vintage floors as the aged wood will have developed a beautiful rich amber glow not possible to duplicate with colored stains - just waterlox or some sort of clear finish is all you need. Sounds like you may not have had a lot of wood finishing experience? You may want to get some quotes if you are thinking of sanding - but be careful of the type of pro who wants to take off too much and try to make it look new. With vintage floors you need to be very conservative about not taking off too much - there's only so many sandings a floor can take. That's why the above poster's advice is agood, about trying cleaning and buffing first before thinking about sanding.