Deductions & credits

My father in law gave it to us to fix up and live in. Once we got into the house we realized that was not going to happen. So we cleaned out and put it up for sale. Never having living in it. It is no closing for 20k less than when his father bought it. This closing happens at the end of this year on the dot. 
I’m wondering what our potential hit is going to be from the capital gains tax.