We had an old IH 4 row planted we used at our old deer camp. Bought it for $125, so we took the chance that it worked. One thing we had to play with was the seed plates. It came with alot of plates, but all of them were too big. It would drop an inconsistent amount of seeds at a time. Sometimes it would have 1, other times there would be 3 all touching. At the end of the day, we were just doing food plots so we didn't care too much. It worked great though, and even with that seeding the corn or beans would still come in great. There were years where it seemed like we didn't get alot of rain, and the corn that was planted with the planter ALWAYS came up good. Ours would cut a "V" in the ground then drop the seed down in the trench. To be honest, the last part that "covered" the seed didn't really work, but the fact the seed was down in that trench still gave it good seed-to-soil contact and the moisture would funnel and collect in that trench for the seed. This worked FAR better than discing/spreading/covering corn.
You don't really know if it works unless you give it a go. I'm not sure what one you are looking at, but ours was VERY simple. The wheels turned and the chains would spin the plates. We did have to replace a chain or two, but those are easy and you can purchase them at TSC.
The biggest thing I would look at is maybe to make sure it raises and lowers. Ours had a long rod that stuck out and you had to pull it. When we did that, it would instantly drop. To raise it, you had to pull it again, then pull the planter about 5-10 feet for the chains to work their way around to raise it. That was the biggest thing we had. I think when we first bought it, the chain to catch that raised it was bent and had to be replaced.