Whether that is most contractors, hiring an engineer, or getting self-educated.

Is in there, but a great thing you can do now is get your "core 4" figured out - agent/lender/manager/contractor - obviously you can adjust this and do one of the pieces yourself (self-manage for example) or don't need a contractor if you do only turnkey etc but getting this nailed down early is key

@Kash Tacke I'm a big fan of ADU's in general especially here in the mid west, yes you could potentially be on the front of the wave, but housing density is the solution to the affordability issue, anytime you are investing with affordability in mind is a great strategy to me, and sound like there are some incentives or at least supporting winds form the local city, that in itself seems like it would be worth at least approaching an architect or contractor to bid up some plans or concepts to take tot he city.  

Basically common contract or agreement law.

Hiring a contractor to assist with repairs and a property management company to manage rental.

One place that will soon become a rental market heaven is an area around Johnstown/ New Albany where a huge Intel plant is under construction with plans for thousands of employees, not to mention the contractors there now. 

---FYI: licensed contractors in our area charge $95-$125/hour.

Expect a custom ADU to take 9–18 months, with 3–6 months for design and permitting and 6–12 months for construction, depending on complexity and contractor availability, and the speed of processing permits.

While we faced minor delays with contractor scheduling, strong project management minimized impact.

In a city like Philly, you will face many challenges - you need to learn the market and know the neighborhood and the block and make sure all of your numbers are within reason, you need very reliable contractors, you need a to understand the permit process, you need to be familiar with market expectations.