Park rules are usually much more restrictive than even houses in HOAs because mobile homes and RVs are close together, and have older residents who are nosy and particular.

I understand the argument that the general public should not be restricted from investing in “highly profitable” deals, but what tends to end up being offered to unaccredited, unsophisticated investors in the “junk” end of the investment spectrum. 

There should be other options, however with an LLC and fourplex - yes, DSCR is by far most likely to be your best option unless you do the heavy lifting with local banks and credit unions (and these are increasingly not great options for this type of stuff as they move painfully slow and are under lots of regulations and restrictions)2) I haven't yet reached out local banks, but seeing the quotes from brokers makes me wondering if Banks may be better? 

No breed restrictions.

Wall removal is better for sale usually for open concept, and sometimes for rentals, but if you want more occupancy (potential rent by room) removing walls restricts that.

I am hoping to find a single family home that I can "BRSTRHHRR" (buy, reno, Short term rent|House Hack, refinance, repeat) by creating a separate living space in a single family home that can be STRed (this is due to local restrictions in my town that prevent STR in multifamily properties). 

.- there is a reason investing in syndication have the restrictions that they do.  

My average fill up is 50 kilowatts so that  $2.00  Two bucks for 200 miles of range with no restriction on speed or fast starts at the line :)  Not every state is the same at our place in Vegas you pay one rate no matter what time of day and that is I think about 12 Cents a kilowat so about 7 bucks to fill up for 200 miles of range. lets say 20 MPG at 3 bucks  thats 30bucks for gas for same range.

If any place has HOA/POA I would be very careful with those restrictions and talk to plenty of people including every board member before buying about their views on STR. 

There are some restrictions so I would encourage you to look into it to see if eligibility applies.