The returns are measured in dollars:  CF, appreciation, etc...and once you recover all of your cost (the faster the better), the return becomes infinite.Let's say you bought a stock worth $100k. 

Hopefully you can rent it and at least recover your monthly expenses .... selling is way too big of a loss. 

So if you're putting over $200k in rehab (still an unknown number), and the property is worth $725k, that means the max you can offer is less than $525...I would say no higher than $450k (I would be very afraid of this rehab ultimate cost).Now, if your intention is/was to refi this property, and you want to recover your rehab cost as well as cove the balance of the money owed, then the total cost including purchase price and rehab, can't be any higher than about $500k. 

I could recover the rent so I applied but they are unreachable to complete their portion.

We just had someone who got heart surgery and recovered at our place.

I was prepared and had data for her to look at, and calculated that we would not only pay off all her expenses, but will easily recover the money in a few months since we aren’t paying those bills anymore and will be more prepared to invest in January.  

Besides, like I said above, in a very short time, the cash investor (DP) should have recovered all their cash. 

Rents don't always rise, I heard that one from investors in Alberta in 2013-2014 and they ended up with negative cashflow when rents went down 20-25% in 2015 and still have not fully recover

Add it to the monthly rent and "forget about it", as we Italians are famous for saying.You will never recover the cost to install separate water meters, a new water main to the building and the cost to install new water piping in the building to divide the piping to two systems.

I don't mind helping them out and I am pretty confident that they will recover after the Chemotherapy, but I guess you never know.There is a limit to what is acceptable.