We need to move my dad into a senior community, we need to find out the rules on selling his house to a relative. Who would we talk to.

Carol's advice is the same as mine. My DPOA SIL consulted an attorney because she wanted one of my MIL's grandchildren to get my MIL's house & at that time, my MIL was going into a nursing home (NH).

I would talk with an estate attorney, as this may affect is Medicaid standing. If the price is fair market, I would not think it would matter. If it's cheaper than fair market, Medicaid may consider a portion of it a "gift." Just to be safe check with an attorney. Either estate or an elder attorney should work, but this seems to be in the realm of an estate attorney.
Carol