To determine the exact standards that you need to conform with, you will need to fully investigate your individual state statutes and regulations and or hire the appropriate licensed contractors and licensed property managers.   

Eviction costs are quadruple the cost as I am required to hire an attorney at 1200+ vs doing it myself for 300 bucks.250 in business fees to the stateEquity loans/refi's/anything of the like falls under "commercial" and is EXTREMELY expensive.

Alternatively, your parents could hire you as their employee to manage their properties (at least here in California).  

I've never personally hired a sub company for a non-owned job over 30k so I've never had the need. 

He wants to buy a buildable lot, seek financing and hire a GC to build. 

lol. that's funny what he said to u.. i am guessing he knows you do all that work yourself, which is the problem. my people were concerned i do all the work. they were super relieved/happy to learn that i hire it all out now.

Let me preface this with I ALWAYS hire someone.

Hire a collection company that works with HOAs to handle the entire case.

One option is to hire contractors that specialize in investment property rehab and manage themselves.

In general I do find quads typically do have twice the cash flow and/or equity gain of duplexes but not in your scenario where the rents of property are virtually the same.From the info provided I would definitely choose the duplex but there was minimal information provided.