You will want to subtract that portion out of the mortgage payment.I have found the 50% rule works better for multifamily.

Costs: Rehab, any expenses associated with filing fees, title company,  attorneys, realtor fees etc.Average rehab 10k, realtor 6% 35k, misc 5k =50k3.Debt attached to the property = any surviving liens like taxes, hoa, violations, violations,  municipal etcNow, subtract the costs and bebt to the final proceed from liquidation.I.e $500k - 50k=$450kNow, we now that your break even bid amount is $450k.This is where YOU come in...ask yourself what is the LEAST im willing to make on this deal?..

Subtract this amount from your offer.  

They said that the gross was about $5500/month which is more than a double of our payment but we will be there at least one weekend each month so subtract $1000 so i would guess 4000-4500 roughly. 

You know how to add and subtract right? 

The Net Sale Price is computed by taking your Gross Sale Price and subtracting your routine “permissible selling expenses.”

Would they subtract $15,000 in repairs and then figure on subtracting 6% from $235,000 which would leave 220,900 as the purchase price?

This is pretty clear and simple with my old way of adding / subtracting but with signing a new lease, am I somehow setting myself up to wipe the slate clean and refund one party leaving?

Then subtract your monthly insurance and taxes (prorate them if you pay multi months at a time), and you'll have your basic CF. 

Just know that when you sell, you'll take the sale price, subtract necessary closing costs, fees, a cut for the realtors, and pay off this balance to the bank.