We' re looking to exercise the option and get financing at 75% LTV fully owner occupied so we can purchase the building and put some cash in reserves. 

These can include -Additional savings or reserves that you, or you co-borrower may have-Proof of payments done on time for utilities and/or rent-A letter explaining how the applicant would be able to make mortgage paymentsFor reference on how to calculate your DTI, check previous posts!

Double check with your lender to confirm.

So After getting this new home, if you can have 3-6 months of payments for each home in reserve, then rent it.

(I will call the actual zoning office to confirm)My question is what should I consider in this purchase? 

1 - Sell the property2 - Take on a cash partner3 - Use Sandwich LO as a strategy4 - Use Seller Financing5 - Use Cash Partner at start and Cash Partner exchange6 - Use Cash Reserve with a Private or Business Loan7 - ... and many, many more

This allows you some cushion to have a couple of appliance repairs or clogged drains and build reserves to paint on tenant turnover.

I confirmed this because a third plumber recommended by the original plumber called us trying to convince us not to pull permits after speaking with the original plumber (they all know each other).

@Dave Foster thank you for confirming that.

That is, aside from taxes and insurance, what are your numbers for vacancy, maintenance, cap ex/reserves, waste management, etc.?