I financed this property using down payment funds from 403B and a local commercial bank.

I think it was for down payment and closing costs.

The cost associated with insurance for not having 20% is peanuts compared to what you potentially can do leveraging your down payment. 

These are features like online renter payments, tenant portal (for payments and work orders), help keeping track of work orders, tax reporting features, and accounting functionality.

You have to weigh the benefit of the insurance claim payment versus potentially having your carrier cancel you and perhaps get black-balled by the insurance industry.

When revenue is low in the first couple of year, so is the interest payment.  

Low or no down, seller financing and low or no interest with a balloon payment later is the holy grail (location, building condition, market also matter but it sounds like you have all that).

If the other two parties want to flip a house maybe they can do just that as partners and then sell you the house which you can buy with a primary home loan with low down payment.

And offset the previous FHA loan payment showing that you're making the payments for it so it lowers his DTI.

., while the average home price is $635,000 (Source) (at a 7% interest rate, 10% down payment, 30-year mortgage that would be $3,802 a month).