I was thinking about adding another garage beside the existing one, connecting them, and adding a garage apartment above them.

A single time... you put 3.5% down, but only have ~1.8% equity, that and the monthly mortgage insurance are how the entire FHA loan program is funded, and it wouldn't exist without that.

You start to see some interesting things when you 'join' this against the city Assessor file, in regards to how many actual units the Assessor is saying exists, and the number of units being licensed through the city.It also provides a road map for violations, and the 'tiers' to work off of, changes of ownership...

You can always file a DBA, if you decide to keep the existing LLC. 

If you used the standard agreement of sale doc used by realtors for PA, section 4(H), it says seller will not enter into new leases, or extend existing leases without buyer approval, so you have your out right there.

Here is one example of how 30K turns into $1800.00 a month or 6% by permitting an existing detached garage into a legal unit.

I have 4 groups all recommended by existing renters looking for houses. 

Is there a lease ammendment that we can add to extend the existing lease?

I would aim to put two rooms in the basement, so curious if I’d have to convert the existing basement windows into escapes or if I could somehow link the rooms to preexisting door.

Am I looking for something that doesn't exist?