First post for me!!

I just purchased 25 acres in northwest Arkansas and the selling agent told me a neighbor wanted to know if we would let him run his cows on our land to eat the grass. Since we don't own a tractor yet I think it's a good idea. The wife doesn't like the idea but since we don't have a way to mow yet we have decided this is the best option.
The guy said he would fix the fence (barb wire) in the one spot that it has a little damage and that he would work something out for exchange of letting his cows eat our grass. My question is what should I ask for or what is the going rate for this kind of thing? There is also a pond and I assume that he will only need to run them on our land for a month or so. We blocked off the pole barn so the cows can't get in it and poop all I er the place. The barn serves as our base when we camp out there. There is no electricity or running water and the barn is the only structure. About 15 acres is pasture.

Thank you for your help.

-Alan