I did just that. Took all my clients from Gold's Gym too!
My place is industrial looking. I'm renting warehouse/old factory space from one of my clients' boyfriend. It's got exposed heatpipes, maple floors etc.
Look around for a decent power rack, a good bench, 3-4 good 7' bars, curling bars straight and ez curl)
Try newyorkbarbells.com. I made a 3" (thick) bar, a 2" bar, I have kegs, sandbags flipping tires, etc.
Do NOT buy 4x6 rubber mats from a gym supply store. They go for less than 1/2 price at a grain/horse supply store. They are called stable mats and it's what the gyms use. Just get 2 for each "station". No need to cover the entire floor ($$$).
Reply back with any questions.