Re: buying land to cash rent out (what do I need to know)
Be sure to get a title search. You want to look at reserved rights, especially gas, oil and coal. If the oil and gas rights are reserved, but are reserved by the current owner, try to get a percentage of the rights in the transfer. If it is a prior owner, just be aware that a well can be placed on the site. If it is coal, be aware that they can surface mine right across your property, no matter the improvements on the site.
Be sure you can get fee title, with no outstanding heirs, etc. Be sure to get a title policy at closing.
As to the lease, trash is always the biggie. Be sure you get a deposit forwarded to you if there is an existing deposit on the lease being held by the seller. Read the existing lease. IF it is a "handshake" lease, the lease is not binding on you and will allow you to renegotiate (formal lease with all the protections mentioned above).
Finally, get an hour's time with a local real estate attorney. A little money spent now can save you a bundle in the future.