That's quite the busy therapeutic center to need exclusive use of the arena every weekday until 7 and the entire weekend. Are they an established business? If not, I'm wondering if they're overestimating the amount of income they'll receive from therapeutic riding once they've run all their boarders off. If they have some sort of business model that makes money, let me know so I can pass it along to the non-profit therapeutic that runs at the barn where I ride. They're very unobtrusive; they serve quite a few riders, but I don't believe they even come close to turning a profit.
I'd be looking for somewhere else. If the board were a great rate, I could maybe work with after 7 pm on weekdays, but no riding on weekends is a deal breaker.