Years ago someone told me that when buying a boat, buy the biggest one you can afford. The reason being that after a short time you'll wish you had extra room for storage, guests, etc., etc. These sage words are still true today.
It is just as hard/easy to learn to single hand a 30' boat as it is a 21'. After all, nothing is really different. However, for that extra 9', you get space to move about, space to store your gear, space for your crew, space to retire to if the weather turns nasty, and the size to handle much heavier seas than a smaller vessel. Lets face it, you are going to spend almost as much time below decks as topside. If you've ever been stuck in a tent with a couple friends during a rainstorm, you'll know what I mean.
Why not purchase a boat that will suit your needs far into the future? As you and your crew become more and more experienced, you will probably want to spend lots of time aboard and your day sails will become 2-week vacations. Does it really make sense to have to go boat shopping all over again?
As far as having $22K to spend, you'll have hundreds of used boats to choose from. I've been single handing around the Keys and the Bahamas for the past 7 years in a Hunter 30.
If trailerable boats are what your looking for, don't overlook the McGegors and the Westerly's, and the other twin-keels.