OK, you get another $.02 worth outta me. A lot of people have chimed in about how expensive insurance would be, etc., etc., but if you scale back your starting plan a little and start with people you know and trust (and even the people they know and trust) you'd be much less likely to be at the receiving end of a stupid lawsuit because someone cut their finger off with a grinder. Friends (and friends' friends) take responsibility for what they do to themselves, and realize that if they're the idiot that files a lawsuit over something stupid, they're the ones ruining it for everyone else (and themselves). This is how skateboarding survived the down time from about 1982-1992. For-profit parks were the model, starting in the 1970s. Fear of lawsuits and the decline in popularity of skateboarding closed all the parks by 1982 or so, with a couple holdouts to the mid-1980s. This, despite the fact that when I and a group of others did research in the 1990s we could find zero lawsuits by skateboarders against parks -- in other words, the fears were unfounded (the economic realities of the decline of skateboarding, however, couldn't be denied). But in the mid 1980s through the mid 1990s, people built their own stuff in backyards and rented warehouse spots. And nobody sued. By the early to mid 1990s, skateboarding had exploded in popularity again, and cities started building public, not-for-profit parks. Long story, I know, but the bottom line is if you at least have an idea of who is going to be using the space, you can be assured that people aren't going to sue, and close the whole deal down. And if you think people's private insurance will sue on their own without the insured person's consent, that never happened with me, my insurance company, and the broken bones and torn ligaments I suffered in the 1980s and 1990s (and 2000s and 2010s).