I usually pay one lb per hive as rent so asking for that would be reasonable. Usually you will get the honey after extraction so you may not get any right up front. Don't worry about them coming by your house or getting in it. They will be too busy to pay you a visit. They may come to your pool if there is no other water source or if they like the water in the pool. I have heard that they sometimes favor pool water because of the chlorine. go figure.
If there are irrigated fields near the hives they will most likely get their water from that...they like moving water (at least mine do)
Find out if where you want him to put them and where he wants to put them are the same place. Important because he will need access to the hives to work them. How long will they be there. Will he pull them in the fall. Get contact info in case you notice something bad happened to his hives. Don't be afraid to ask him anything about bees.
Lastly, thanks for letting him put bees on your property. It is a huge help to us beekeepers and the environment when people allow for bees to be spread out.
Life is tough, but it's tougher when you're stupid.” John Wayne