I agree with buying used if you want to go the gym route. I did... Probably spent less than 10% of what it would have cost me to put a comparable facility with all new equipment. Don't skimp on the cardio though. That stuff takes a beating and used cardio will be like owning a Triumph... They'll always be in the shop.
I don't really use gym equipment so much anymore though. If I were to open one today I would open an "express"
Go Performance and Fitness franchise. You could fit it in 800 square feet and for under $10K fully outfit it with the type of equipment they use (not your typical gym). The link I just gave you takes you to the full franchise description. You will have to call Jared (the founder) to find out about the "express" version. Let me know and I will send you his contact info.