How can I go about this

[Leonardo Martinez]

I have a potential deal that the owner owns the house but still owes the Lot.

Seller has agreed to pay taxes that are due and also pay off the lot when He gets cashed out.

How would the purchase and sale agreement would look (in regards of the wording)or what paper work would i need to have in writing that she will pay off the Lot and taxes at closing or after getting paid?

All information provided is welcomed !!

thanks in advance!!