In a well-designed arrangement, the agent's incentives are aligned with the owner's. Both of you, for instance, want to get the highest rent possible without scaring off prospective renters by overcharging. A good pro will know when it will pay to accept less rather than risk going vacant for a week.
Although the commission is negotiable, keep in mind that the agent will represent other properties and, given a choice, will steer prospective renters to the units that provide the biggest income and rent with the least effort. You might give the agent extra incentive by negotiating a sliding commission that would pay more if your rental income exceeds a given threshold. You might, for instance, pay 20% on the first $10,000 in income, 30% on anything above that.
Be sure that the agent will advertise the property on the multiple listing service for rentals used by all agents in the area, and that other agents will be provided a healthy slice of the commission if they bring in renters. Again, you might try to beat the average.
Also be clear on the duties your agent will perform. Those should include vetting prospective renters, arranging for cleaning and inspection after a renter leaves and sending in a handyman for such things as a plugged drain.Your deal with the agent should also allow you to seek renters on your own. That will save you on commission costs and spur your agent to beat you to the punch in signing up renters. Many owners advertise on sites such as Vacation Rentals by Owner. Because prospective renters going to your VRBO site will see your competitors' properties, it would be worthwhile to set up a website of your own on Facebook or a similar service. You can use that when people respond to your flier on the office bulletin board, for instance. The key is to hustle. If you get a kick out of running a little enterprise, negotiating and keeping track of details, renting out a vacation home can slash your ownership costs. If the thought of all those chores makes you shudder, maybe owning a second home is not for you.