Back taxes owed, 2 weeks till tax sale, how to structure?

[Troy Sheets]

We came across a homeowner that has roughly two weeks till her house goes to tax sale. She owes ~$15k which would obviously need to be paid before the tax sale. It's unlikely we could close on the property in two weeks as it's in a trust (inherited the house from her mother) and she can't find the paperwork. How do you suggest we structure this? Get it under contract and pay the back taxes, I get. How do we make sure she either follows through with the sale after we've paid or we can at least recoup the money we spent saving the house? Ideally with some sort of penalty/interest? We'll have our lawyer structure this but I'm curious what you've done in similar situations?