The first time I never had contact with the appraiser and with the refinance a formal appraisal was never done.

@Max CordovaHave they set up the 1031 exchange with a qualified intermediary?

However I don't think this is likely as I'll have neither a credit score or history of income (either in the US or in the UK) and don't have enough cash to purchase somewhere outright and doubt I'd qualify for a regular residential mortgage.

This opportunity may not be available in the future bc the credit union doesn't use credit score to qualify you just payment history and DTIThanks for all your help.

Basically the duplex is for her but she would not qualify for a loan herself so I would be a co-borrower. 

Some lenders say that if you only rent it out a "little bit" then it can be a second home, but won't specify how much out of the year would qualify as a "little bit."

"Homeowners' ExemptionThe California Constitution provides a $7,000 reduction in the taxable value for a qualifying owner-occupied home.

So it qualifies as a replacement for the 1031.You just have to ask each syndicator if they can or want to accommodate you as a tic to the LP.

The lender you're talking to is obviously limited to conventional financing and you won't qualify there.  

As a first time home buyer, I qualified for a USDA loan.