It's probably fine and good for the land, and I'd rather think the better of people than the worst, but if you wanted to be cautious:
Check they are insured.
Consider if you want them on the ground over winter to prevent it getting poached and give it a change of recovering. Some people also use this as a way of ensuring there's less chance for them to claim grazing/squatters rights. And bear in mind that the longer the tenancy, the more likely they are to want to maintain it.
You may want something about any improvements that can be made, that they need your permission, and if any compensation can be made for this. Do you want the tenant to improve the fencing, can they do it to a suitable standard, and what will they want in return? Can they erect a shelter? Are they expecting the water as part of the deal and a reduction for if it's not there?
If you decide to continue the arrangement, 3 years is the norm for reviews, and it's worth getting a proper tenancy agreement sorted.
Not sure if you claim any BPS for the land, but you want to make sure you keep them rather than them attempting to claim them or do activities that are not allowed (or just don't want). And for any restrictions from any schemes the land is in
They'll need to sort out a temporary CPH number too.