Am I nuts to consider this circumstance where a in-home provider and his currently healthy mother (92) move in?

My father is a widow and disabled with limited ability to walk. Otherwise he is quite healthy and mentally sharp for being 88 Y.O. He lives in California. He has been living alone at home with daytime in-home caregivers from a local service for the past two years. The number of folks that cover shifts for my dad, and the occasional person who is a no-show makes the level of care he is receiving very inconsistent. Also to go form P/T to F/T care through a service is very expensive. We (my sister and I) moved him to an assisted living facility two months to try it out as he needs someone there at night as he is a fall hazard. He wants to move back home. I have POA. I contacted his church and found a person who was a live-in assistant/caregiver who is now available as his client passed away last month. He comes highly recommended and my father knows him. He is in his mid 50's and his 92 Y.O. mother lives with him. She is in good health and still drives a car. She has been living with her son for the past 10 years. If I retain him to be a F/T live-in helper for my dad, he needs to bring his mother with him also. The house is big enough but I am looking for advice on if there is any type of legal agreement template available for a live-in with this room and board (rent credit) arrangement plus a salary? I also would want them to sign some sort of a liability waiver if that is even possible. Am I nuts to consider this circumstance where a in-home provider and his currently healthy 92 Y.O. mother move in? What are the kinds of issues I need to ask them about and try to include in an agreement we both sign? I want to protect my dad as much as possible from liability where pit exists, and have some sort of a written arrangement. Any templates available for a live-in agreement where it is not an agency? What are the biggest liabilities for my dad under this scenario and is this arrangement uncommon? I need some advice. Thanks in advance to those who respond.