Is it common to have colon polyps in your 20's?

Possibly: We don't really know because most people don't get colonoscopies in their 20's. Most people start at age 50 for colon cancer screening. There are some inherited syndromes like Familial Polyposis that predispose someone to polyps, but they are exceedingly rare. The polyp should be biopsied to figure out what type it is, which will be very informative.