Your obstacle is that most people are either too busy or too lazy to work out. Once they come to that realization, they don't want to pay for something they won't use.

The key, then, is to get them to use it. My suggestions?

1. Jacuzzi with a beer vending machine nearby.
2. One free 30-minute massage per month for all members (look for relatively new massage therapists looking to build experience and a possible clientele, and be willing to replace yearly). The masseuse should probably be hot.
3. Hire hot chicks to work the facility while wearing tight workout clothing.
4. Profit.

Step 1. Steal underwear
Step 2. ....
Step 3. profit

Stand out front of McDonalds, laughing and pointing at fat people while wearing an ACMY shirt.