You will need an ASA bareboat certification (or equivalent) AND coastal navigation certification to charter from most places in North America (at least places I''ve looked at). In fact, most places will require you to have bareboat even to charter a 27 foot or greater boat just for the day.
So, in the ASA system, you would need to take the following classes: 1. Basic Keelboat; 2. Basic Coastal Cruising; 3. Bareboat; and 4. Coastal Navigation. 1 and 2 are prerequisites to 3. You can also combine them all into one class and get levels 1-3 done in a week, while cruising on a boat in a beautiful location.