Easement Purchase

I am in negotiation to purchase an easement for $300,000 to construct a digital billboard, upon receiving all approvals. What should be included in the contract? I have hired an attorney who specializes in billboards, but have never purchased an easement. When should the payment(s) be made if I receive all approvals, etc. My thoughts are subordination approval, line of sight, non-disturbance, just a few points. What is my down side to an easement, besides a large payment upfront. Rent Roll should be $15,000/month conservative. Or sell to large company and collect rent. What other issues should I be concerned with? How do you feel about easements? How do you value an easement?

Before you move forward on this project, I would urge you to call me at (573) 535-0206. There are many, many things you need to be aware of.