Anyone that is looking at your assets is always going to need to factor in property management, so you can show that as a real expense (and really make it as high or low as you want).I work in a vertically integrated real estate and development company, and I cannot imagine how things would run if we did not have an internal property management company that essentially works for the other companies but also stands on its own.

Obviously I want to keep my costs low but still want to spring for amenities that would give me a competitive edge compared to other rentals.

The 6.75 rate is a conventional 30 year w low closing fees (the credit union I used last time).

So assuming your son has low debt, then he should be able to qualify for a house in the low $300K range. 

I don't work in Nashville area but $165 per sq ft seems quite low to me.In terms of financing, I would speak with a few construction lenders and also hard money lenders.

The value of your SDIRA may be too low, but I'd recommend Gary Mobbs at South Star Bank in Gonzales, TX.

Honestly, I think you're estimated expenses are a bit low.

We look for good school systems, low crime and desirable neighborhoods.

Down payment of $13K including reserves sounds pretty low to me . ( Based on Maryland )

Myself, I specialize in Section 8 and low income properties.