I would insist on either higher than market rent, a non refundable option fee, or a higher than current market price for the purchase option.

As far as making it advantageous to the buyer, if I were the buyer I'd insist on no prepayments penalties from day one and the ability to prepay in almost any amount.

She insists it's stable but I've never worked with this before, and am wondering if there are any risks I need to be aware of?  

If you insist on doing this at least do a background check to make sure they do not have any prior evictions or terrible credit.

That's fair to you and only an unreasonable seller would insist you pay an amount that's far beyond fair market value.

I usually run into to problems with USDA which insists on a Deed Without Warranty which is an issue in Texas

The seller refuses to allow an inspection because he insists it’s a waste of time and money and the home inspector is not qualified to determine the serviceability or life of the mechanicals.

LLC Loan: Documents insisting on waiving rights (state: PA)Loan documents I am being asked to complete require signing away many rights.

You might need to talk to a lawyer if they insist on you paying.

I once had an obvious leaking water heater, yet they insisted on sending a plumber to inspect, who said "yep you're right, it's shot".