We have offered cash for keys before and each case varies with the tenant, current rent, our motivation to get them out etc… Your friend simply needs to look over the lease because the new owner must abide by it. In short there may be a new landlord but all the terms of the lease are the same so your friend is okay. Also with regards to showings and such, the lease should specify what can and cannot occur with regards to marketing the property. In “general” a 24 hour notice is required but leases vary.