Earlier quoted context omitted.
Selling children and guns (at least in most parts of the world) is just outright prohibited. Selling land isn't. You don't need to figure out whether it is an illegal or legal child sale as all child selling is illegal. Selling land in itself is not illegal.
Its outright prohibited to sell illegal land as well. Facebook might also require a proof of ownership before allowing the sale.
It’s strange that multiple people on this thread have gone with “prostitution, slavery, sales of firearms don’t happen on online marketplaces, why should this?” It’s so obvious - those are obviously illegal. Any reasonable human being taking a look at a gun sale post can tell that 1. It’s a gun and 2. Guns shouldn’t be sold here. It’s so obvious that it can be trivially automated too.
Please respond if you can verify pattas in a reasonable amount of time. Because boy do I have a business idea for you.