It sounds like you already made your decision and really just want to know how to sell without loosing your positive cash flow in the duplex.
If that's the case, you can ask your tenants to prepare for the home insurance agent visit (who is actually your realtor) to take great pictures (at least 25 pictures of inside, outside, neighborhood and street views to be put in the Multiple Listing System (MLS)). More pictures - more sales.
But, ask the tenants to be neat.
Then, when selling, have the buyers drive by (without disturbing the tenants message in the MLS),
and, if the like everything, the buyers can make an offer subject to preview.
This means that you first agree on the price and terms of the sale, then the property is shown to the buyers. If they change their mind after previewing the property, their escrow money is refunded.
If they like it, they proceed with the closing.
If priced correctly, your property will generate more interest and "traffic" amongst prospective buyers.
Make sure that your property is marketed extensively on the internet.
Beachfront Realty, Inc.