I agree with what almost everyone above said. Refinish the floors.
You can rent a "U Sand" machine from Home Depot and you really can't mess it up (unlike a belt sander, this is lighter grade and uses 4 orbiting sanding disks). Sand it for a few hours (or get a high school kid for $10 bucks an hour) and put on a dark stain. The bad parts of the floor will look like awesome character.
I think whether selling or renting, this is the way to go. If you rent it, and the renter is stupid and scrapes a huge dent in it, or spills some red wine and doesn't clean it - just take some sandpaper, some stain, and varnish and in 10 minutes you fix it. If you use Laminate- your tenants WILL scrape their Grandma's antique china cabinet across it and ruin it. Your laminate will last 2 years. Your hardwoods will last until you sell.
Oh and if this is a lower class rental - by all means, paint the floors. It will take one hour, cost $40 bucks, and you'll be done.