The units will be 20 wide by 30 deep with no garages (600 sq ft a floor). 

I’m a week or two out from starting demo and site prep for a brand new double wide.

Maybe have a discussion that you are afraid she can't afford the rent, and you are considering giving her notice because of this (this nips off the "I'm a bit short" excuses)  along what would be necessary for you to be comfortable allowing her to remain as a tenant (catch up on the behind rent, maybe over 3 months period  AND all occupants PASS background check) . 2-3 working adults SHOULD be able to come up with the rent -- I don't imagine that you are gouging anyone.It is possible that if there is a wide open door in front (no 30 notice required if you move in the next 45 days!)

The field is wide open.

It has wide appeal and will never produce negative comments or reactions from buyers.

Prices will vary widely and you need to know why that is.

In Pennsylvania, that term can be used to refer to a wide range of area.

Do most PMs have a company wide policy that owners must agree to on reserve amount?

A 30' wide lot being 8' or so narrower and eliminating the driveway is big. 

Well without question, your returns are higher when you leverage.Also to consider...if you are buying $50k properties, please have your eyes wide open and expect to deal with the problems that come with those properties.