These USPS leases can be a bit different from regular GSA.Check out this list of USPS https://about.usps.com/who/legal/foia/leased-facilities.htm

I'm a member of GaREIA, they have a google group where experienced local inveztors trade tested (and mostly reliable) contractors, legal helps, strategy.   

@Darrell Kirby no approval is necessary.go to: https://www.michigan.gov/mshda/rental/housing-choice-voucher...https://www.affordablehousing.com/list-your-property/

I don't think any lender will approve you if you are trying to buy multi-family in WA as your primary residence with your work being in located in CO.  

Additionally, local real estate meetups and events can expose you to financing options, legal contacts, or strategies that are applicable no matter where you're investing.Remote investors often build their teams by reaching out to local agents, property managers, and contractors in their target markets.

What is my next step in the process to legalize it?

A house in rural MO, like my mom's, doesn't require any permitting or zoning approval at all.

But depending on the case, the tenant can be responsible for the legal fees incurred.

He's still legally responsible for payment, right? 

The loan approval is based on the property’s cash flow—so as long as the rental income covers the mortgage, you’re in a good position.