The best way to do this is to renovate a unit or two to the specifications to bring it up to market.  

Simplify the structure as much as possible, have clear roles and responsibilities that are not overlapping (meaning only one person is allowed to make certain decisions) and a clearly defined exit plan.

As far as I can tell, I'm the only REI in this specific niche within the county.

You’ll want to check if your specific work falls under their home improvement contractor licensing, or if there are additional local permits required depending on the county.

It is also great to change small but specific terms and conditions due to it not being just one tenant anymore.

If I were you keeping the property as 4 units and renting out bonus unit under the radar may be your best option especially if you plan to refi or do HELOC while occupying. 

Feel free to reach out if you have any specific questions, as an investor or a lender happy to share any advice I can!

Did USAA give you a specific list of renovations they want done?

Rent control laws are market specific.

For commercial buildings, be very specific - price range, $/door max, unit count, unit mix, part of town.