Typical cost for the setup would be in the $15,000 range which would include production of the Private Placement Memorandum, Subscription Agreement, and Operating Agreement, Investor Qualification Forms, as well as filing Form D with the SEC, and state “Blue Sky” filings in those states where your investors reside. 

Typically it would be the tenants responsibility to provide access.

I do not have a traditional W2 job so I can't pursue the typical conventional loan or a FHA since I don't have income (hence the DSCR route).However, I've seen that most DSCR lenders do not lend if the loan amount is less than $100K.

In general in single family zoned areas, JADU typically subtract value (I suspect largely due to the OO requirement).

I researched commercial construction careers, and found a construction degree is typically required.

Issues 1) even garage conversion ADUs in single family zoned areas typically cost more to build than the value that they add.  

So, a house that would typically cost $100 per sq. ft. to build 5 years ago, is now costing $200 per sq. ft. 

They'll typically leave behind mattresses, couches, broken furniture, rotten food, etc.

Mortgages for LLCs with personal credit under 680 are tough and expensive, and under 640 are typically not really economically practical for the borrower. 

Look into connecting with some local investors, they typically have meet-ups often and swap stories and different strategies.