Hi Richard, Do you currently own/operate LTRs?

Yes BofA is all over the country but if you go to your local branch it's pretty likely that loan officer and/or office wouldn't be licensed to operate in another state. 

I own and operate a property management business serving these areas.

I've been doing this 20 years, so know how to operate these.

Estimating is both art & science and FWIW most professional estimators rarely get it spot on, usually operating within a Delta.There's tons of estimating books, software etc.

Once you get organized and get the process down, placing tenants shouldn't be such tedious work.

.- Put Upward pressure on real estate operating costs: Increased costs for raw materials and supplies, and the likely increased costs for labor involved in many real estate related CapEx and maintenance projects signal the risk of increase in costs for real estate operators.If there is no impact on near-term supply, a modest slowing of inbound (illegal) migration, more reason to believe that the cost of many goods and services will increase, and real reason to believe that inflation triggered by something other than an increase in the money supply (namely the cost of specific goods and services that are NOT housing going up, which comprise the CPI) will force the Fed to raise rates, this, on the whole, is not good for real estate investment returns. 

So your 35% operating expenses makes sense and seem plenty conservative to me.  

Does anyone recommend knowledge sources on building a mobile home parks (websites, books, organizations, plans, etc..). 

You will be going up against larger operators with bigger budgets and more experience.