I would make ready the unit and rent it.

Cap rate is the standard used for large multifamily - 5+ units.

I've had nothing but tenant and property management issues for the MFH units I own.

If anyone who runs a successful flip (5+ a month) or LTR (50+ units) has time to chat I would appreciate the direction and reassurance.

The current owner lives in one unit, and rents out the two other units, WELL under market.

So, if the office is vacant the appraiser may have identified the property as being a single family once again because that was probably its original permitted use.Also, I wouldn't call this a duplex as that usually implies 2 residential units to most people.

Having lived in one side of 2 unit for 10+ years, therefore more than the 1 year expected occupancy to satisfy 1st mortgage, now wanting to rent both 2 units to tenants for long-term rental 12 month leasesdoes the original occupancy satifiy the HELOC if there is any type of requirement?

So you purchase properties and you have someone interested in leasing from you and then arbitraging the unit with your consent?

I highly recommend you get connected to a property manager who manages section 8 units and utilize their experience to scale at your pace. 

The rent in summer was 1500 per unit after minor renovation.