Free markets are designed around a selfish ambition for making money. You can only make money by pleasing your customers. And hence free markets are the greatest mechanism for prosperity.
There's nothing wrong with making money that way.
Are you sure?
Like, say, the tragedy of the commons?
For example, we are running out of fish in the ocean from overfishing. But there's no shortage of cows and chickens, despite massive consumption of them. The former is the commons, the latter is private property.
Much like how there isn't any reason you have to pay for food in principle. It could become so cheap and easy to produce, say, bread or cheese that it is available everywhere at no nominal cost.
So yes, you should. You already do, realistically.
Slightly more formally, an assertion of exclusive property rights is a sufficient condition for something to be closed access, but it isn't necessary.
Though, admittedly, that does depend on what one's definition of a free market is. Is it unfettered commerce, consumer protections and suchlike be damned? Is it a system of commerce that ensures equitable access? I'm personally of the mind that, as long as I trade with certificates that bear Caesar's face (or trade with proxies for such certificates, like a MasterCard), he gets to make the rules in exchange for my being able to lean on his legal system to protect my interests, so I find that the equitable access angle is nice.
(Likewise, trading with Bitcoin or Ethereum or whatever the in-vogue cryptocurrency is today means that the code makes the rules, and I get to pay for the privilege of having my transactions indelibly entered into the distributed ledger and for the code governing those transactions to be buggy and exploitable. I'm still scratching my head at it.)
At the risk of building a strawman here, I'll caution that it's logically inconsistent to expect the state to enforce exclusive rights while also urging that strict regulation of a shared commons is an illegitimate market intervention.
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0: That is, unless the title holder grants license, but that's a whole other conversation.
It is a minor point I suppose, but this is the other way round, because Caesar makes the rules you trade certificates that bear his face. It takes vigour and energy on the part of law enforcement to stop people from moving to private currencies.