BRRRR Analysis Question - MAO to Factor in HM Debt Service?

[Jon Mason]

I've always done my BRRRR MAO calculations like so: MAO = ARV * .7 - rehab costs - refi closing costs.

About to do a BRRRR with HM and after doing some googling I saw some folks include the holding costs (seemingly including debt service) during the rehab period in their calculations. I'm struggling to do that math in my property analysis. It's like a chicken and egg sort of scenario...I need the debt service amount to come up with the MAO, but I need the MAO to get the loan amount in order to arrive at the amount to use for the debt service. Hopefully I'm making sense. How do you guys handle this?