Illegal money is counterfeit money that is made by someone other than the Federal Reserve.
When you make counterfeit money you commit a Federal Crime and if caught and convicted you can get several years in prison.
Illegal money can also be money that was obtained illegally such as drugs and money laundering.
Some examples of illegal activities that generate money illegally would be the sale of drugs, illegal gambling, bribery, and illegal kickbacks, or theft.
Essentially any movement of illegal proceeds from the illegal source to a legal source is money laundering.
It's not legal to make your own coins and doing so can get you into trouble for counterfeiting.
If you print your own money then you can be charged with a felony for counterfeiting and with making the money and use of counterfeit money if you used it.
If you get caught printing your own counterfeit money then you can be charged with a felony and serve several years in prison.
If caught printing your own money then you will have a federal felony arrest on your record, making it very hard to get a job.
In other words, you can't get something for nothing, at least not if you are trying to do it by counterfeiting.
Although it is easy to print your own money, it never works when you try spending it.
If you just printed money though to use for a game at home then that would not be illegal as long as you don't try to use the money.
Producing or using counterfeit money is a form of fraud or forgery, and is illegal.
The business of counterfeiting money is almost as old as money itself: plated copies (known as Fourrées) have been found of Lydian coins, which are thought to be among the first Western coins.
Under federal law, the use or attempted use of counterfeit currency is illegal if the person has the intent to defraud the recipient.
A conviction for producing counterfeit currency similarly carries a maximum sentence of 20 years imprisonment and a fine, as does a conviction for merely possessing counterfeit currency.
Counterfeiting Federal Reserve notes is a federal crime.
Possession of counterfeit United States obligations with fraudulent intent is a violation of Title 18, Section 472 of the United States Code and is punishable by a fine of up to $15,000.00, or 15 years imprisonment, or both.