Your concern is warranted on the commission but please consider this. What is the qualification of the tenant?? Does the tenant have a exceptional credit, a very stable work history and a very clean rental history. If this is the case and you feel the prospective tenant is overly qualified and will care for your property as if it was their own you may want to consider paying a "FULL MONTH'S commission.
Either you pay on the front end to not have to pay on the back end, doing so will help the remainder of the rental lease go very smoothly.
RE/MAX Realty Group
Many agents do not do rentals simply because it is not worth their time to spend X hours over X days showing X homes, all for a paltry $500 to $1500. Keep in mind that what the landlord pays out to the tenant's agent as a commission is almost always split with the agent's broker, so the agent is not keeping all of the money. I know quite a few agents who charge one month's rent for their services as a listing agent plus a half month's rent for the tenant's agent/co-operating agent. They don't do too many rentals, but they don't really want to do rentals in the first place.
You have no obligation to pay any commission/half a month's rent at all, but you also might lose this tenant. If the tenant has good credit and a stable job, then you might want to consider working with the tenant's agent. You'll have to assess the risks versus reward of letting this potential tenant go versus waiting for another viable tenant to come along. If you have to wait another month or more, you will then have just paid one or two month's of your mortgage, thereby effectively erasing any "savings" you might have made by not working with the first tenant's agent by paying the full commission.
I think you'll also have to assess if the tenant's agent is going to truly do all of the work necessary to see the job to completion or if he/she is going to remain in the shadows of the transaction.
If you cut the Realtor out of the deal & rent to his/her prospect then I would think he/she would go after your renter for commission...if they had an agent agreement.