It depends greatly on the state in which you live and on whether or not it is your first offense. I will speak as if it your first offense. I know that for posession, of a small amount without intention to distribute, in Pennsylvania can result in up to two days in jail, about $1000 of fines, and six months of probation. I have been told that selling can result in up to year in prison years of probation and thousands of dollars in fines. While these seem quite extreme, they do not begin to touch on the subject of what can happen after you finish with paying fines, prison term, and probation. You will have a felony record, making it difficult to get a job, get financial aid for college (or a number of other things), immigrate to another country, run for public office, etc. But, police can be quite fickle, and if you're young and it's your first offense, especially if you live in a college town, there is a very good chance you'll get charged with a disorderly conduct have to pay a $300 fine and then you can go home.