I recently purchased a used spa on E-Bay and have learned quite a lot about the used spa area.  Take the time prior to purchasing a spa to look for internet resources and learn of the problem areas that involve the spa world.  When I purchased my used spa, I had no idea what to look for and was taken for a ride.  It eventually was worked out and became a good investment.

Remember that if you have a good shell and are handy with tools and plumbing that you can repair.replace the motors and pumps for about $700.00.  Also a good cover is worth it's weight in gold.  Make sure that you have a good cover to conserve heat and water.

Along with the cost of the spa itself, you need to remember that the installation is very important.  Expect to spend about $500.00 on a professional electrician to install the wiring and breaker panel. 

Save yourself alot of aggravation and RESEARCH the purchase first.  It will make you wiser about the problems of a used tub and help you know the questions to ask the seller.