I am a contractor so I got started with a mechanics lien and well the cash flow was nice.

I don't know the arragement you have with your family friend, but if you don't bring cash to the table, it is going to take A LOT of successful flips to keep you housed, fed, and clothed, unless your friend wants to run a charity.I have a full-time mechanical engineering job in a chemical plant.

I doubt I"ll ever allow myself to really retire.I'm a mechanical engineer by education and work in the commercial utility business (power plants). 

I don't have rehab experience but have been a maintenance manager, and an hvac mechanic/contractor for the past 10 years which give me a good head start in dealing and working with contractors.  

If the structure is built exactly to spec, you don't need this.Engineers like those at ATSFraming inspection, plumbing inspection, and mechanicals inspection (called "Framing + MEP Inspection) right before you call for the city's framing inspection.

You probably have to have a licensed electrician, plumber, and mechanical guy, but probably only one.

The owner had passed away so its not like anyone had an emotional connection to the house.Surprisingly the house was in good cosmetic condition considering it was vacant but all the mechanicals were old. 

I am a elevator mechanic by trade, and a home owner.

Make sure that the all mechanical systems aren't from that time.

I just recently advanced to Mechanical Journeyman and am feeling ready to get into the market.