But, many Realtors say that financing is not in their "wheelhouse" (granted, we are trained that way), but it leaves such a wide gaping hole in strategizing. 

Ive seen many youtube videos where homeowners lost big bucks b/c drainage systems didnt work....be it interior..or exterior.

There are a few holes and things missing, but you are on the right track.The biggest issue that I see with your plan is that the family member is putting up the down payment and putting the mortgage in their name, but they aren't seeing a return on their money for at least a year.

The property could become an endless rabbit hole where the investor keeps dumping money in with little to no results.

Walking distance to the local watering hole?

I still get them in my house and I've been sealing holes for almost 30 years.

I 3-hole-punch the lease and add it to a big binder.

I have read through the beginners guide, and chased a few rabbit holes linked from that.

By the time I take out money for cleaning that he never did and holes in walls from hanging stuff and any thing else that he did/didn't do per the lease he may end up with getting back $150 or so.

For commercial roofing there are pre-sloped foam segments that will put a very slight pitch on the flat roof to allow better drainage as well as creating an insulated system.