Certification and/or license requirements ...
Well I'm not doing it solo, I'm taking 2 friends and a a family friend who has years of sailing experience in yachts. I'm('rents are) buying a Jeaneau 36i which seams like a reasonable boat to sail. I've sailed 75 ft boats but the Mediterranean was pretty calm when I sailed there.
If you go back and look at your original posting, it looks like you are planning on a solo trip aboard your Sonar 23. I think the answers here are based on an assumption that you have some sailing experience and are looking at expanding your sailing horizon. Their is a huge difference between sailing as crew on your parents boat and being skipper of the boat.
As I, and others, have indicated ...
Sailing is a pretty unregulated sport. You don't need to have any specific certificate of training or license to buy or sail a boat in most areas of this country. Some states may have requirements for a boater safety course and that requirement often depends on the size/type of boat and the size motor/engine it has. For MA, you can find the requirements that cover you at:
http://www.boat-ed.com/ma/index.htm
Having said that, the boat "owner" may find that their insurance company may offer discounted rates if they have taken a specific boater safety course. Your parents' insurance company may have their own rules that cover when, where and who can operate their boat.
ASA and US Sailing are two organizations that represent boaters at the state and national level when new laws that affect us are being considered. They also have an educational mission and earning a certification from either indicated you have completed a specific course of instruction. They are not
required in order for you to sail your parents boat. They do have value as a measure of your formal training when the time comes that you try to charter a boat. A license
is not required in order to sail a boat to any given destination.
There is value in getting as much formal training as possible but it is not required to sail to the destinations you have indicated so far.