I agree with hellosailor. We took an ASA basic keelboat sailing class two years ago and then promptly bought a Catalina 27. The sailing class was definitely worthwhile. We're still learning, but the class got us sailing comfortably in a hurry.
We love our Catalina 27. She's definitely a great starter boat, IMO. Very easy to sail. The older ones are not very expensive, so I would definitely do some comparison shopping to see what else is out there.
If you are concerned about expenses, you should realize that the purchase price is just the start. Next is insurance and slip fees. Then there is the steady flow of "boat dollars" required to maintain a boat. And, of course, you will soon want to start fixing her up. (Currently on our list: replace the lifelines, add a bimini, roller furling on the jib, etc....) Not saying you shouldn't do it, just make sure you understand the full story.