One Man Demo Tools?

Hi all - Might tackle some various loose stone & retaining walls around my property. None done properly, just stacked garbage.

Really basic/ignorant question, what are the tools or machinery I can get to break up large pieces of ledge stone that I can't pickup or move? I've tried chisels and sledgehammers with no luck. Tempted to buy a pick axe and rotary hammer but wanted to ask here first.

Unfortunately I can't afford proper professionals and good materials (gotten quotes ranging from $37k to $66k); and the work of those I can afford is sketchy at best. Rather tackle it all myself slowly and with good products.