What exactly is this other person doing that earns him or her half the profit?

Unfortunately, the man who turned my eyes to this business and was beginning to guide me recently passed away, and I am at a loss for where to turn next.I am interested in finding a good REI group in the greater Washington DC area; one that requires little or no cost to attend the first few meetings/get-togethers.And even more than this, I am seeking a benevolent knowledge-giver who is willing to impart their precious experiences to me; in exchange I will do whatever I can to be half as useful to them as learning from them would be to me.

In a sweeping generalization of the past few decades, the "left" half of DC's map has for a long time been considered wealthy, safe and profitable.

But yes, it's the last affordable bit of SF, and by affordable I mean half mil for a SFH.

The paint is in OK shape except for an 8-inch hole in the living room drywall, and some chipping around the window sill where the seller had taped giant plastic sheets (???).

Go to the courthouse and plan on spending some time there, half day to start.

With your 2 properties one vacancy cuts your income in half--a big hit. 

Half the battle is educating yourself before taking the plunge.

The house needs everything: Roof, gutters, siding (asbestos shingles nailed over older cedar shingles), drainage abatement, rehabbed bath, total kitchen, replaced flooring (half), refinished flooring (other half), back steps, total landscape, HVAC (old furnace is missing), insulation (2" in attic; none elsewhere) additional electrical circuits, plumbing includes iron pipes, interior trim and paint.

You can end up paying half your profit in tax if you are successful enough to be in a high tax bracket.