@Mike Hoskins Could you buy the property from them and have them rent from you? It seems like a good property if you say appreciation was great. just rent to them to cover all your cost and use this as appreciation play to help them out. Eliminating realtors, the costs should minimal. They can then use the money to do BRRRR. They bring the money, you do the work and split 50/50.
If they dont want to do BRRRR after couple deals they have enough money to do what they want. If they want to downsize they have the money to do so, then you can sell it, hopefully it appreciated and enough principle was payed down that you can profit or keep it and rent it for market price. If they want to buy back the property they should have enough to do so, sell it back to them for the remaining principle and they pay all costs. If they want to keep renting from you they have the money to do so.
At the end of the day no matter what route they take, you will have BRRRR properties without putting any of your own money in.