Building a new ADU will put you in a more “negative equity position” than converting a garage for example, which only cost <200 per sq ft.  

Now if your interpretation is cash flowing enough to quit your job that is another conversation.  20 or 30 properties at 1k a month a door, if managed properly is a great revenue mark in my book. 

Written policies are necessary when you add employees to aid with training or enforcement of standards.I would focus on adding doors to your management company.

Try to get a garage if you can. 

Found an awesome deal on Craigslist and it allowed me to get my foot in the door with an investor (owner of the property I arbitraged.)

Quote from @Chris Seveney:If the front door works - then technically it is turnkey. 

We are in a safe community, so tenants can choose to leave the door unlocked or hide a key under the mat.

I'd be looking at multiple structures. we try to build below the average new build cost in our market in Columbus Ohio which is 515,000 last year and we target land 40-50k and urban core adjacent where we get higher price per square foot. we build for clients with margin around $190 a sq ft depending on multi or single. we can get that down in our triplex it's a little higher on our single family homes because of garages and limited economies of scale. hope that helps. idk Philly but if you show me the area and styles of homes I can give you some more insights. 

~225k per door

I helped a client purchase an SFH fixer with a detached garage.