I'm interested in finding more information about renting farm land. It seems like this could be a good option for long distance landlording since there's really no upkeep necessary with renting an empty field. I do have questions about how to find renters, how to gauge market rent, how the deals are structured etc.
I own (and farm) productive crop farmland in the midwest. Due to the high price of land, I'm not aware of any locales where land be bought and rented for cash at a rate that provides a return that's favorable when compared to residential or even commercial real estate rental.
As others pointed out, the taxes and insurance on farmland are often VERY low when compared to real estate with structures, but the cash rents are just not sufficient to cover the mortgage payments if you are buying at today's prices. As you point out, there's little upkeep "required" on land. But the downside is, as investor, you lose the benefit of depreciation which is basically tax deferral (at worst) and tax avoidance if you are willing to hold the asset till death.
Finding land tenants and gauging market rent would not be difficult. In fact many states publish details records of farmland statistics including yields, cash rents, soil types, etc.
Many farms are rented on a cash basis, but many are still sharecropped as well. The land owner will often pay for 1/3 of the cost to put out the crop, while the farmer puts out 2/3. The proceeds are then split the same way. Subsidies from the government may be split along the same line, or they may be kept by one party or the other. An arrangement like that allows the land owner to take a little risk with the hope of a return quite a bit higher than a cash rent(which carries little risk) would produce and it serves to align the motivations of both parties.
You may assume that farmers would always be motivated to produce the highest yields/returns possible, but that's not always the case. And you may assume if you are getting cash rent, you aren't concerned with the farmer's yields. But...if a farmer is cash renting land that isn't owned by himself, he's not necessarily motivated to keep it well drained, fertilized, sprayed, etc. When soil quality is neglected it can take a few years of treatment to rebound to it's full potential. A farmer who knows what he's doing cash renting from a land owner who does not, can be a recipe for manipulating yields(in reality or as reported) to make the land appear less productive than it is. Crop land enrolled in any government programs requires yield reporting. All the farmers in the area can find out how that farm has produced over it's history. What they'd be willing to pay to buy or cash rent the land for will be artificially deflated if the operating farmer has been neglecting the soil as part of strategy to reduce his cash rent or buy the land at a song. Because only he may know what kind of time and money have been spent maintaining the soil quality....he's got the upper hand on the landowner and all the other farmers in the area.
OK, those are some potential pitfalls of a landlord unfamiliar with farming cash renting land to a farmer. But sharecropping by splitting costs/revenue basically forces you to keep VERY close tabs on exactly what your sharecropping farmer spent and produced and sold where that land is concerned.... or to trust him completely. Your farmer is likely running a farm that includes more than just your land. He's got lots of other expenses related to his own land that can land on your desk, for you to pay 1/3 of. And unless you are following the grain truck to the market, you have no way to know that several hundred bushels of your corn didn't wind up as feed for HIS cattle.
What I'm trying to say is, I'm interested in farming land for you if you happen to buy any near me :) Just kidding. I am saying be careful.