That piece is often underestimated by many.For the other key numbers:The structure is  Maximum Allowable Offer (MAO) = ARV - Holding Costs - Rehab - Closing Costs - ProfitARV (after repair value based on recent sales within a 1 mile radius.

What should I be careful about compared to buying an existing property, and are there any key differences? 

I’m patient enough to wait for that.

He's patient and kind and transparent.

Key tips include:1.

Yes, it's a lot of work but it's a lot of key data.

Once that is complete, allow them to work things out as long as you get the keys to rekey if you will (and I would) near/at the end of the month. 

I can message at any time, call for a one on one phone meeting, and get educational materials that key me into things that I can't find any where else.To be in this program, I first had to demonstrate my competence and be invited, go through a rigorous in-take interview process, and then pay the entry fee.  

Another thought I had was to keep the same pipes but put meters at key parts in the piping where I know it is dedicated to a specific unit in the house.

I think you're missing a key ingredient: how much time do you have to earn your 20%?