That's a long time - and a lot of cash now - but consider inflation, in 30 years it's be worth like < 1/2 as much as today.
I'd want either a short contract or a requirement that the amount increases by 2% or something to adjust for inflation.
Otherwise by the end, you're the chump getting paid peanuts.
Also I'd find out about transferability and what happens when you sell the land - does the contract automatically transfer etc.
This is where the future value of the payment becomes an issue
