All conventional mortgages should have identical underwriting standards.  

Always confer with a lawyer, particularly one who specializes in this type of knowledge as I have come across ones who are just as ignorant about these laws and regulations. 105 CMR 410.000 MINIMUM STANDARDS OF FITNESS FOR HUMAN HABITATION940 CMR 3.00 3.17: Landlord-Tenant254 CMR 7.00 Apartment RentalsMassachusetts General Law Chapter 186Massachusetts Security Deposit Law: One of the most neglected rental laws in Massachusetts and one of the most disputed between landlords and tenants.

Not sure what B2Rs lending parameters are but you should go talk to local banks and see what they have to offer for commercial loans.Your deal is doable but not shiny by commercial standards.  

Do mortgage rates for FHA/ VA not change with credit score, while the standard 30 year does?

To invest you don't need a lawyer Reg CF filings to solicit unaccredited investors are all standardized to protect investors just make sure they filed and read the filing.

Each of these must meet certain standards before FHA will insure a loan. 

We have several Mh that have connected septic tanks that we have had a clearance letter for but the county is saying that the state will deny that and we need to bring it up to 2022 standards which means we can not have shared systems.

Conventional is still better, for now, but my lenders are still in the mid-7's and upper 7's at par pricing, meaning no buy downs or rate adjustments.Flexibility - Many believe that rates will recover in the next 2-5 years... or thereabouts... the 3-2-1 prepayment gives a lot of flexibility compared to FRM lenders where 5-5-5-5-5 or 5-4-3-2-1 are nearly standard prepayment penalty structures.

@Colby Zeller FHA has standard table to calculate MIP on Loan to value  and type of amortization.

You have to abide by the USPAP standards and part of that is a competency requirement.