Chris, I haven’t used First United for a duplex, but do have experience working with them on traditional mortgages and to be honest I’m not surprised they got their info wrong, their knowledge and customer service isn’t the best (and their website isn’t user friendly at all) I would definitely talk to other banks.

It might be easier if you had more space rented out, and a good broker might be able to help you.

Talk to a Mortgage Broker, not a bank.

You just need to be speaking with the right brokers. 

Other fees may include appraisal, processing, application, etc - so it's good to know these details up front before you decide on a lender based on interest rate alone.Also, keep in mind if the lender is a Broker or Direct Lender (brokers bring deals to direct lenders and add their fee on top of what they would charge = more expensive for you).

Jobs that I have considered include property manager, leasing agent, broker, home inspector, and of course, real estate agent.

But what I meant is not much info about them online from customers, such as reviews.

Work with a good mortgage broker who has multiple lenders and programs.

From being on the other side....owner and broker endorsements go a long ways.

I'd recommend speaking to a mortgage broker who can explain your options.