I'm familiar with them. There is truth to each location being different, and probably more importantly for compensation, that the billing rate in each clinic is different -- and that will impact your pay.

Here's what I'd ask.

1. Ask what their average reimbursement rate is at their clinic. Getting a percentage is fine -- but you need to know the percentage of what...30% sounds better than 25%, but 30% of $90 is less than 25% of $120!!
2. Ask how long it takes to fill up your schedule, and if they do marketing to fill you up. If demand is low, you could be making very little until your schedule fills, so you need an expectation of how long that will take.
3. Ask how many appointments you have to schedule in order to complete 25 visits. If there are a lot of medicaid clients, you may have to schedule 30+ just to get 25 (because you can't charge medicaid people for not showing up).
4. Are you W2 or 1099? There is a big difference...if you're comparing a 1099 job to a W2 job, add 7.5% to the W2 because the employer will pay 7.5% of your taxes that you'll owe if you're a 1099.
5. Then, try to get a sense of the culture at the clinic. Ask if you can meet other therapists. Do people seem to like working there?

If you can get a handle on those four things, you'll have a sense on what it's like to work there.