If it was a written lease and your grandfather was in compliance with it (e.g. had never defaulted on the payments--which he would not have, if he prepaid--or violated any other terms of the lease), then IF your grandfather is still the tenant/renter, the lease is still in effect. A landowner can only sell what he has, and that means that when there is a written lease, what the landlowner has to sell is land with a tenant, where the tenant has certain rights (i.e. to use and possession) which therefore limit the landlowner's rights and control. So the property would be sold subject to the lease; selling land does not end a lease unless the lease contained a term stating that it did.However, a lease is not a deed; it is a contract, and is personal to the parties to the lease. If your grandfather passed away, for example, then the lease ended when your grandfather died: a lease does not survive the person leasing it, and there is no right to inherit a lease. Or if your grandfather is alive but no longer the tenant on the land (for example: you are), the lease would only be in effect if the lease could be assigned (the terms of the lease did not prevent assigning or transferring it) *and* it was legally transferred to you in writing (again, while your grandfather was/is alive). On the other hand, if your grandfather stopped being the tenant without assigning the lease to anyone, passed away without assigning it, or if the lease contained terms barring assignment, it would not be in effect.If the lease is in effect, the tenant can sue in court to enforce it: e.g. for a court determination that it is still valid and a court order that the landowner honor it.