I am in Cincinnati, where duplexes generally sell for less than single family homes.  

When the property sells, They get a check at closing for their principal and interest.I ask them if they want to loan their money on another property.

All agents are incentivized to sell it's a transactional business and because you are just starting out and in a low barrier market you will encounter many new agents who need to eat and pay for their gym membership and car that month.   

If the traditional model is used, hypothetically if gross commission for the whole transaction was $10,000 split evenly between listing and selling agent, each side would receive $5,000.

Sell it in two years.

Of course, they also offer an unparalleled warranty on the notes they sell, so that is probably worth a premium.

For an exchange, they want your intent to be that you hold the property for long-term business or investment use (for both the property you sell and the property you buy).  

do you sell the duplex to pay off the mortgage or what do you do?

We might break even with selling the house even though we have also made some good updates to it. 

I have seen a lot of flips in my neighborhood and the surrounding communities, but some are taking a while to sell as many are priced significantly higher than the median home values on blocks that just aren't there yet.