I’m about to start the process of getting a permit so that I can rent it out as an ADU. 

Same folks who approve building permits etc. or they can tell you who to see. 

Well I've been kicking myself over spending $230 on a pro membership instead of recreating the calculators.

He/she can also manage several projects at the same time that are not necessarily being done by the same GC.Each GC must be licensed and insured and will be responsible for pulling all permits and hiring/managing their employees and subs.Some of the CPM responsibilities would be scheduling, budgeting, selecting finishes and meeting up with GC in a regular basis. 

And while you are delivering pizzas, you can be on the lookout for vacant houses, or permit violations, and the like. 

Note that the additional option I presented is 100% predicated on doing everything above board, permits, plans approved, lender scrutinizing and approving every little thing, bla bla bla.

This may be why the bank doesn't permit utilities to be restored.  

There is residential land, agricultural land and recreational land for examples.

These are generally pretty painless to acquire.You may need a general contractor's license to do certain renovations on a property - particularly those requiring permits.

Hi BP,Found out today while filing for permits for a garage door replacement on our recently purchased SFR here in Southern CA. that the shed we build didn't comply with setbacks and the city wants to do a code inspection in 2 days due to suspicion of us trying to rent a 720sqft permitted addition in the rear of the home built before we purchased.