Send an email to your chosen city's  planning department asking them what is required to change the basement to an ADU.   

You might need it to be approved by the fire department, water department, landscaping approval, parking, zoning, etc. 

@Ethan Daniel DacarI'd start by reaching out to the permit department to ensure that you need a permit for the work you are completing. 

I will check with my Urban Housing Development department to see what are my options.

Typically you should shop around and ask for the commercial lending departments. 

Are there any investors that will fulfill the Tenants request to be paid to depart?

@Ciro Cuellar You'd have to check with your local zoning department to see what you need to do and what types of permits you have to obtain in order to move a mobile home rental property on that particular piece of land.

My kids are going to medical technical school learning how to shut life saving machines down when connected to dear old Dad!!

Tenant can stay for free, borrower/landlord can ask for forbearance and hang on for dear life.

I Think every municipality is different and you should speak to an attorney or call the building department for a definitive answer.