He has another lot that he wants to build on at some point, but doesn't have solid plans yet.

A majority don't even make it 18 months from shiny new license to toes-up in the parking lot.Leaving the relative security of a 9-5 W-2 job - especially one with benefits - is a risk that should be undertaken only with a solid plan for surviving startup. 

However, I have done a ton of reading and have built what I would like to believe a solid foundation for real estate investing.

Although we likely find better deals than OOS investors with our relationships, you can still purchase solid deals on the MLS that produce 10% cash on cash and in areas that are gentrifying and growing.

The rehab was super manageable and presented a solid opportunity to cashflow higher than 30% CoC.

They'll likely be able to give you some solid numbers for vacancy and management fees and any other costs you need to consider in your market (hazard insurance, lawn care, utilities, etc).

But I am in need of finding a solid/ dependable General Contractor or construction team in the Philadelphia area.

Then the owner decided to sell anyway. price went from around 350k to a sell price of 780k.Last I looked at the house it was solid as stone, 15 years later.

The root cause of the foundation problems is possibly the expansive clay soil.

I would consult with a local draftsman first and foremost  and come with a solid flowing plan.