Can I sell a penny for a trillion dollars if I find someone dumb enough to buy it or is there a law against it?

I would say the odds that there is a law against it are about as likely as finding a person that would do that.

A trillionaire isn't dumb. They didn't get there for nothing, so that scenario combines two unlikely things... and if they were to sign something that agrees to that they being a trillionaire would be able to find some way to fight it in court.

I have seen stuff like that on eBay on a much smaller scale... a person selling a link to something rather than the object itself... in really fine print.

I wouldn't do any of that because who knows what drama they go through trying to make a quick, easy buck.

Unconscionable terms in an agreement can be tossed out by a court The real problem you'd have is if the person is "dumb" enough to agree, did they have the mental capacity to consent? It would be like signing a contract with a child. It wouldn't be enforced.

Generally speaking there are no laws against it. Buy low sell high, it's the American dream. And there are lots of rare pennies that people pay big money.

There are laws against fraud. For example, if your taking advantage of someone who clearly isn't smart enough, or someone who is drunk. Or if you represent yourself as a coin expert and sell them a fake coin.

So yea, it would probably be illegal.

Depends on what country you are living in.

But in the US, no, unless you tell the person something fraudulent.

Well, it almost certainly violates fair trading laws, since you would have had to either explicitly or implicitly misrepresent the value of what you were selling, and anyone connected to the trade other than the purchaser could very likely make a solid case to get it reversed by questioning the competence of the buyer. But you're not going to find anyone outside of a hypothetical who has access to a trillion dollars, and even bringing it down to a reasonable amount, anyone intelligent enough to have amassed a fortune is not going to be stupid enough to part with it that easily.

What you’re not going to find is a person with a trillion dollars.

There is a law about fraud so if you are knowingly selling that penny that is worth very little for an excessive amount by stating it is a very rare penny, especially if you have doctored it up then yes you are committing a crime.