How to custom renovate

[Lizina Green]

I am mid-way into a reno flip when a buyer states they want to purchase the property at asking but they want to pick the finishes? I did lower the purchase for them to take the house As-Is and they could finish it but they didn't take that.

How do you structure this?

What do I need to do to protect myself?

I am not even sure this is a good idea. This my first flip and I do not have a lot of cushion in my budget.

Thanks