Paying for rehab cost. How to get money back at closing?

[Joe Sanchez]

I’m in Texas and have a family member that wants to do some renovations before selling. Me and my partners will pay for the rehab cost and want to know how to get our money back at closing. My questions are:

How are my rehab cost plus “interest” paid back to me at closing?

Is the seller responsible for all the taxes if I’m being paid?

What type of deal is this called?

Thank for the help!