This will typically be a DSCR loan up to 75% of the new value.

I would look at the DSCR loan as the first option.By the way, I suspect you are going to be disappointed by any refi appraisals   ADUs typically appraise poorly   JADUs can lower the property value Vs having the space as part of the primary unit.  

Which size of home is typically perform best on a cost benefit analysis?

The Midwest, including cities like Detroit, offers some of the best opportunities for affordable properties with strong rent-to-price ratios.

I will post back tommorrow after I get details of offer. 

.: Its typical for real estate investors to hire a private home/building inspectors to inspect a real estate property before they buy it.

The additions they put in to make extra bedrooms take away the standard livable areas you would find in a typical SFR.

I've never asked them to be my mentor and they have never offered.

It seems to me that if I were the agent on the buying/selling side of these, I would save 2-3% on each deal (typical agent commission for each side).

I will say anyone offering this should be giving you all the pros and risks of the flint marketplace.