Fix important stuff like the roof, siding, doors and windows.

Might as well get to an even better position if I’m going to need to build more wealth in either scenario.

You're going to need a lot more than "a little bit of insight".

Obviously, there are minimums since the cost of a roof or rewire doesn’t change with the ARV.

I only know the big companies and they're quoting a lot higher than I usually pay here for similar roof. 

The seller agreed as long as we agreed to the asking price, there was a patch needed in the roof and a door had to be replaced.

To be totally frank you are going to need to adjust your expectations or abandon your plan. 

I made minor repairs to mechanicals and replaced an aging garage roof but didn't really invest much else.

could it be the roof valley?

You are going to need LOA, full seller financials, executed purchase contract, POF,  HUD showing all costs coming out of proceeds, various other addendums (depending on lender/investor) and you will almost always need to prove that the property was MLS listed for some period of time with a realtor.