Radio Tower Lease with Tear Down Home

[David Wright]

Hello,

I've read several posts related to cellular tower leases and there's a site that gives you the ranges ($350-$4,000) of monthly leases. However, I am looking at a property with a large Radio tower (75; tall and suspension wires that cover a large portion of the yard). This tower sits on a mixed-used property with a home that needs to be torn down. I would plan to build some needed storage (not self-storage) buildings for my personal use.
In reviewing the easement agreement it appears that one of the earlier landowners must have sold the lease for a flat fee back in 1998. It is in "perpetuity and assignable", so no recourse of any kind with any future land owner. However, there is a stipulation that if the Grantee leases or licenses to space that the Grantor (land owner) would get 20% of the profits for anything over $15,000 annually. This would exclude calculations for any increase in maintenance of the tower, which I'm sure the Grantor could stack the deck.
My belief is that is a very one-way contract. However, I am curious if anyone has some knowledge of what a Radio Tower may lease for (monthly/annual)?

Thank you