the answer to that is maybe...if serving and repairs are included, also end of rental removal then it might be right for you. keep in mind that stairlifts do limit access on the stairs...those "this will change your life" TV ads are done with staircases that are much wider than standard. rentals are usually only available for simple runs of stairs, straight or with a standard wind and no access problems at either end.
Personally I would steer clear of used unless they are manufacturer reconditioned with a comprehensive and decent length guarantee....too easy to end up throwing good money after bad.