As far as upkeep, most of these lots are already in unimproved land, where everything around is also unimproved. Road access is usually at least there. So, no mandatory upkeep except looking at satellite photos once every couple of months. Some places have tax, I think an average would be maybe $50 a year, if any?

I don't know about little, but I regularly see plots of land (sometimes developed) in remote areas on Facebook Marketplace for really good prices. Or at least prices that seem compelling to me.