Additional Rent Revenue

[Drew Forte]

I currently have a 65,800 sq. ft. warehouse with four tenants. One of my tenants has asked if they could put a storage unit outside behind their space since they are out of space. Would it be unreasonable to charge them a fee although they would be getting the storage unit? My thought is there will be wear and tear on the concrete. Trying to understand if this is a good idea and if I could possibly create a little extra revenue. I'd appreciate feedback/advice. Thanks.