HI Bridget, OUAT I had an SDIRA and loaned some money to a flipper. Skip to the end and I wound up owning a floor to ceiling storage unit masquerading as a SFR. Since I didn't have the emotional/family tie, I feel qualified to give you this piece of advice. RUN. If you must help, do the legwork to find your father a reputable outfit that grooves on taking this type of property and making it shine. Be prepared to be shocked by the low, low price that rehabber will offer him to buy the gem. They will have a lot of outlay on their plate to get the house back in fighting shape. Since it's 70's vintage, there may be MANY other capex issues not mentioned in your narrative. I was fortunate in that some wonderful folks here in Texas took pity on me. I am happily severed from my "Learning Experience" and it is going to be ready to go on the market in a couple of months. Again, if you can, take your Dad, and your "Family Home" out of the picture and do an objective analysis.
All the best to you and keep on looking!
~Bob