It is a new market for me, so I will want to visit at least once to see with my own eyes, but will not do any supervision of rehabs. 

I have only charged for the locks being changed on the property when the previous tenant moved out because she said it took too long to get the repairs done even though I told her what your plumber said about the floor being warped and I believe he was correct because it just seemed to me like foundation issues in certain spots that couldn't be helped and I did also charge for the steps being replaced  with 2 boards which probably measured about 6 ft in.lenghth $450.00 to be replaced  and painted because that was another tenant complaint and you told me to go ahead and fix it....I told you said that when we looked at the house when the tenants moved out he also didn't see any work that needed to be done to it...the only thing i saw was the rat droppings and the garage door issue that didn't work and the limbs down in the front and back yard which i requested to be removed.

I don't think the new owner is under any obligation to refund anything unless its specifically documented ahead of the close.

For most newbie that needs actual visit to the house then they need traditional way.

However, there were other jobs ahead of mine and water leaks are a priorty over broken sewer lines. 

Even if it's just adding insulation or doing the painting at the end, you should determine how much involvement you are able or willing to take on ahead of time based on your budget.

We never approved these repairs as we were never told ahead of time. 

What's concerning is the subcontractor stated he wasn't getting paid by the GC yet still visiting/"living there".

I can say without a doubt that I would have totally taken the wrong deals if I hadn't physically visited the area to get a feel and built a team of professional boots on the ground who weren't afraid to be blunt with me. 

First, figure out what your focus is and then go full steam ahead.