So you're walking down the street, minding your business, and you spot a $100 bill or a nice watch. Can you just keep it? I mean, they do say 'finders, keepers,' right? Well, the law in New York is very clear about what actions you need to take if you find lost money or property.
New York Consolidated Laws, Personal Property Law - PEP § 252 addresses how a person should handle finding lost property. The law states,
Any person who finds lost property of the value of twenty dollars or more or comes into possession of property of the value of twenty dollars or more with the knowledge that it is lost property or found property shall, within ten days after the finding or acquisition of possession thereof, either return it to the owner or report such finding or acquisition of possession and deposit such property in a police station or police headquarters of the city where the finding occurred or possession was acquired, but if the finding occurred or possession was acquired in buildings or on grounds or premises under the control and supervision of the commissioner of general services as described in article two of the public buildings law, then the property may also be deposited in a station of the capital buildings police.
So, long story short, you must return the money or property to the owner, or if the owner is not known, it must be turned into the police within 10 days of finding it. If you find any lost items outside of a city, you can turn it to the state police, sheriff, or the state park police. You can also turn the property over to the owner of the property where it was found. For example, if you find a wallet at an amusement park, you can turn it over to the park's 'lost and found' office for them to deal with. If you decide that you aren't going to return the lost item, you could be charged with a misdemeanor,
any person who shall refuse or wilfully neglect to comply with the provisions of subdivision one or subdivision two of this section shall be guilty of a misdemeanor and upon conviction thereof shall be punished by a fine of not more than one hundred dollars or imprisonment not exceeding six months or both.
Keeping lost property isn't anything to play with in New York State unless you're willing to risk your freedom or money for it.