A general valuation formula many in the industry use is: # of economically occupied lots * monthly lot rent * 70% (assuming 30% of income goes to expenses, common for parks on city utilities) * 12 (months in a year) / desired cap rateFor this park at a 10 CAP (many parts go for lower cap rates now, but small parks might still go for a 10 CAP), that makes: 21*298*.7*12/.10 = $526K . 

Is it possible to also write off the other common deductions (PMI, interest, depreciation) while living here? 

Some people like the 1 LLC per property since its common to name the LLC the street address for the property. 

506(b) is quite common if you have a preexisting relationship with investors and do not need or want to publicly advertise. $150-250k is a pretty small raise for a syndication, though.

The most common portfolio style loan in Texas is a 20 year adjustable rate loan.

Is it common to just put the rates up to what you wish on buying the property.

Please be mindful of scams!

I used to think real estate investing was a scam and now I can prove that it works to help people achieve their investment dreams!

Does each family member own an undivided interest as tenants-in-common in the property or is it owned inside of an LLC or other entity? 

In regards to inflation in your commercial leases, there is a clause that is commonly used called "Indexed Escalation."