I belive your conforming limit for a 4plex is right around $750k for your county. 

If it has been truly shut down for 4 years (defined as no customers, no marketing, etc.) then it may have lost its grandfathering (legal non-conforming) status and may not be allowed to be used as a mobile home park anymore.

There is also a portfolio product that I am aware of for primary home buyers that only required 5% down on a multi-family - but you have to be over conforming limits with this product.

I look for the strictest rules in the area and conform all properties to fit. 

Did the city say that your property is zoned for 2 houses on a lot of your size or it is a large enough lot that it could still be conforming if you subdivided?

I understand that to mean a conforming loan.

I had hoped that I would be able to use an FNMA conforming loan, but I don't know if they would ask about the source of the funds if they are seasoned (my understanding is two months).Thanks again for your feedback!!!

I self-financed the deal by pulling cash out of a US property through a refi, 3.5% 30year conforming.

They want things to conform to what they already know.Air BnB is a great idea and seems to have an overall positive outcome for those involved.

Until I sent him the reference, he thought such a loan was non-conforming, but in reality what he thought was Fannie Mae's rule was actually just a lender overlay.