You'll want a DSCR based approach with someone who understands the father/son arrangment and underwrites it no differently than a normal tenant/landlord relationship. 

BRRRR is the way to go.Additionally, a good Turnkey company will walk you through the purchase and Closing process, show you the rehab, connect with your Lender, Title company, as well as either directly lease and manage the property in-house or arrange for such.

I've been contemplating on whether or not I should move my sights out of town for my next property.

However this doesn't take into account the search, analysis, arrangement of PM, etc.

I would like to buy the land and build a retirement home, contemplating renting out for a vacation home prior to living in.

I call my mom and arrange for her to watch my boys (twin 3 year olds) over labor day weekend while my husband and I get the place cleaned out, painted, and carpet out and ready for the flooring. 

Also, in a small multifamily you are more likely going to need to arrange some sort of lawn care since the odds of a tenant taking this on are less likely. 

I would definitely suggest you take a lot of pics when you see the property or if you have enough time arrange for a contractor to come with you so he can walk the property and talk to you about what repairs are needed.

We had contemplated it and our investors knew in advance it was a likely outcome (if we couldn't get conventional funding).  

How is a deal such as this structured; what parties are involved in this type of arrangement; what costs are associated; are there specific covenants or terms that need to be included in the contract; etc?