I want to ensure that I follow any sort of regulations and safety standards but I don't know where to even start or know how to estimate rough costs.

Happy to provide some insight on the state of the STR/MTR market here as regulations change drastically from city to city. 

I saw those regulations too and forgot when I was considered from an investor's perspective.

Seattle has become more lenient on ADU regulations because of the housing shortage. 

In this contract she could sell it for practically nothing and I still pay her $4,000 the same amount. 

Also keep in mind that adding sqft will likely increase your taxes and local regulations might limit the use of the ADU. 

Louis offers affordability, cash flow potential, and emerging market opportunities but also presents management challenges, unfamiliar markets, travel costs, local regulations, and crime rates.

The laws apply to owner occupant but puts fear of regulation into any lender. 

A detached quad consisting of four one bed one bath units will cost significantly more than an infill quad consisting of four one bed one bath units etc..Lastly, there are very few zoning districts in Philadelphia that would allow for a 4 unit building to be constructed in Philadelphia on a parcel that is only 1,000 SF and from a practical standpoint the units will be quite small when you consider the need for open area and common halls/stairs.

note some localized regulations require creativity to envision