I'd recommend looking at costs. your build cost is going to be well over other homes because of the fixed costs like slab, Hvac, roof, etc. check the market drivers and weight the benefits of short term versus long term. long term is no furniture and help pays mortgage but at this size it doesn't really cover everything. we didn't find a lot of economies of scale in single family detached. can you build more than one unit?

However, I still struggle to understand the art of estimating rehab costs. 

Typlcally, a lender is going to lend 75% - 90% of the Cost of the project (property price plus rehab cost (scope of work)) or 70% - 75% of the ARV (As Repaired (as completed) Value).

For residential multifamily properties (1 - 4 units), can you use a home warranty to take care of the repair costs associated with rentals?

But I'd like to see Lynnette's projects to support your claim "the portfolio was a 30% increase in cost to the consumers" since in TN, NC, VA, NC PPAs are priced at avoided costs. 

If it costs $100,000 to install an ADU and it rents for $1,000 a month, then it may be worth it.

Meaning, if you take the money only, you would have depreciation recapture from your cost basis up to the original purchase price of the building (not including the land cost because it wasn't depreciable), plus a capital gain up to the insurance proceeds.Hope this makes sense. 

The larger the purchase price the greater the spread you need between purchase price plus holding costs plus rehab cost and ARV.  40k projected profit on a 600k project is too skinny for me. 

Roll them all up and the averages are:purchase $154krenovate $47Ksell $232kThese are gross numbers, not including closing costs, borrowing costs, holding costs, licensing and permit costs, G&A, overhead, commissions, forward rate buy-downs, and lease-up fees, to name a few of the many expenses incurred. 

My son currently lives in the townhouse b/c he is going to school and works in the area.Since he is young and starting out in life, I would like for him to only cover the basic costs (taxes, HOA, utilities) just enough for me to break even (I believe that will put him slightly little lower than market rent rates).