Is it possible to buy and sell publicly owned land? Heard of a profitable little business with someone doing this, paying little actual costs, and reaping the benefits of the sale. Is this hearsay or factual?
It's hearsay.
Government departments that own land sell it from time to time. MOD, NHS and Local Authorities the biggest disposers - they do it through land valuers and offer for sale by private treaty or auction. But that's hardly 'public land' - it's land owned by public bodies.
Common Land, Village Greens etc. cannot be sold.
So what sort of other public land could you be talking about?
Sometimes you can get parcels of land on a housing estate for example,that have effectively been forgotten about and nobody actually owns. I know of someone who had some such land next to his house,he fenced it off,tidied it up and went through the correct procedures to acquire ownership. Apart from legal fees,I don't think he actually paid a penny for it.
I'm assuming it's very rare to find land like this,but on paper it can be done.
You could mean " adverse possession",which ,as far as I understand it ,means fencing of the land for 12 years.
See what "Google" says about adverse possession.