Sale of Billboard Easement

[Joseph Pisano]

I am looking to sell my billboard easement in Southern Texas. All expenses are paid for by Lamar. Its a new 20 year lease with 20% monthly gross revs. I am being told I can sell for near a 6% cap ($17k/m). Are there any comps I can look at to see if 6% is too low? I view it as a NNN investment.