Most of my BRRRR projects have infinite returns since I don’t have any money remaining in the deal.  

Properties where the prices have been lowered and yet they still remain.

Remaining are cosmetic deficiencies and nothing functional.

Do you use the national inflation rate?

It already has tenants, and my plan was to help the owner out of his tough situation by seeing if he would take the amount of his original loan (divided to pay off the remaining balance of the loan) so he doesn't have a foreclosure on his record, and would give plenty of room between that and current valuation.

Use the remaining tax free money from your sale and invest locally with it so that you can keep an eye on what is happening in your market. 

Since the property is currently rented at 5,500/mo - paid up through July 31st with a 5,500 deposit too; my broker/agent wants me to refund remaining months after closing; likely March 31st.

I've been reading up on rent control and I see that according to new laws, I can only raise the rent up to 8% max to account for the 5% increase and inflation. 

Stock market (index funds) return an average 7.5% adjusted for inflation so I believe if you're doing REI, at least shoot for something higher than the market. 

I'm not interested in moving there - it would need to remain a vacation home.