I'd get a roof rack before I get a hitch installed from Uhaul unless you can't lift a bike overhead. Over all cost is the same, maybe slightly more going with the hitch.

Also remember that if you are ever rear ended, the bike might not be covered under your part of the insurance since its not "bolted" to the car. The other guy would cover it...maybe.

And the added hitch is mounted to a frame that isn't designed for impact so can bend the car frame pretty bad as well.