Land isn't necessarily easy to sell. If I were going to do this, I'd buy land that's uber-popular. For example, lakefront property in a prime neighborhood.
Yes, you'll need insurance, though it won't cost all that much. If someone were to come onto your land (even without your permission, even if you've posted no trespassing signs) and hurt himself, you could potentially be sued. This is especially true if you intend to allow others onto your property for the aforementioned money-making ideas.
I have problems with hunters coming onto my land without permission. They leave a mess (for example, five deer minus their heads), and they shoot where they please. We used to be able to catch them pretty easily: we have only one road leading into the property, and they'd park their truck there at the entrance and walk in ... now they have four-wheelers, which take them into the woods, and we don't always know they're on our land. It's scary to think what could potentially happen; we're located within a mile of a school, and bullets can travel a long distance. These hunters are brazen and will lie to your face: "Oh, I have the owner's permission to be here." "This is my uncle's land." "I've been hunting here for years and no one's ever said anything to me!" Okay, that last one might be true.
And don't underestimate taxes. $100/year sounds impossibly low, and I live in rural NC. I own 45 acres of farmland, and even with a HUGE portion of my taxes deferred because the land is actively farmed, I'm still paying a good bit more than that.
And, yes, be 100% sure of the zoning. I would be more willing to buy land in a neighborhood than rural, raw land. Neighborhood lots are more likely to sell.
And be sure of what regulations you're agreeing to when you buy. For example, if a developer wants to get a neighborhood up and running, he may require that you build on your new land within X number of months. Some land can only be divided X number of times (that's a big one out where I am because they're encouraging people to keep family farms intact instead of parceling them out among 8-10 cousins). Land can be restricted in ways you might not imagine.
Overall, I don't think this is a great idea.