Mixed-Use Property with 2 separate dwellings

[Katie Sax]

Hello! I am trying to see if I would be able to use any residential loan package on the following property. It's 2 units, 1 parcel, zoned mixed-use. One unit (1700 sq ft.) is currently leased as a commercial office. It's still structurally a house, a non-profit just moved desks into bedrooms. The lease is set to expire December 2024. The other unit (950 sq ft) is a detached garage converted apartment. It also has a lease set to expire June 2025. Lease termination is an option for both, but I'd like to let the office tenants have until December, if possible. 

The properties are taxed as one, zoned as one, etc. But, they are structurally separate and both income-producing. My plan would be to occupy the small apartment unit, and utilize the main house for my small business. However, I could also do the opposite if necessary to secure the loan. This is a really great long-term investment in the details, so I'm very flexible with what needs to happen to get the property. My realtor is also business acquaintances with the sellers, listing agents, and tenants, so we have a lot of room in negotiating things to make it work, if it's possible. 

I'm sure there's a million things I've overlooked, but first, I'm wondering if the "back house" would be considered within the same one unit as the main house for conventional lending? 
I've spoken with a few lenders, but I've been told my only option is commercial. So, of course, if you have any information on a loan option that would avoid a 20% down payment, I'm all ears! TIA!