Except its a heavy renovation, and its a conforming duplex.

Those numbers may change my answer but I THINK I say go for it...4 unit (largest you can get that still gets a conforming mortgage, get a 30-year loan, live in one of the units, get the hang of it and repeat a few more times. 

It's a legal non-conforming use because the duplex use predated the zoning code.

Sometimes states follow the federal laws in terms of things like depreciation, and sometimes the states do not conform or have not gotten around to mirroring the federal laws. 

Their are some non-conforming lenders who may work with you on this but you terms and pricing are going to be higher.   

If they took 20,001 sq. ft. or more in this example, you now own a non-conforming lot, which can add even more potential challenges down the road.Spending some money on an attorney now could save you a lot of problems later.

Property is a single parcel with 3 lots and is zoned Single family with a legal non conformance for the duplex."

Will you be using conventional/conforming loans or portfolio loans? 

.- You have to be a member- They will be more likely to do non-conforming loans, which means they'll have their own standards for lending and may be a little more lenient.Most likely you'll need to do hard money on a low end property. 

I do new construction but only on owner occupied. 95% on conforming and 80% on jumbo