Ultimately it’s personal preference but if you choose to proceed without permits you should at least use trades who have the ability to obtain permits in Philadelphia.

It is a way of building long-term wealth by using the power of leverage to hold wealth-building assets long enough that they eventually pay for themselves, thus giving you the ability to use other people's money to acquire assets you could not have acquired otherwise.

(Assumable loan, Waterfalls/Hurdles, Ability to model a JV) I've come across "Synthesis" by Sharpline Equity.

I have seen a lot of strong market appreciation as well so the ability to buy and renovate for a good ARV still remains. 

In return, I'm confident in my ability to find deals and manage the rehab process.

For something like an ADU it's surely going to be cost prohibitive.If you want to buy a cheaper property with your 1031 that has the ability to put an ADU on the lot. 

Very true, you make your money when you buy and that formula is dependent upon your search abilities, how big of a net you cast to find opportunities, your negotiating skills, your ability to identify great locations (often near good schools), and your ability to transform the property.

When you move out of the city, the debt on the current house will negatively affect your ability to borrow to purchase a different place.  

I never imagined I would sell or refinance the 2 best ones because I have 2.65% mortgages on them and they cash flow well, but want to make sure my equity is working up to it's ability for me. 

Some of this comes down to lender overlays and their ability to work with you on the documentation.