I disagree with those that say you can't find a boat for under $20K that would be suitable for your requirements. A decent older 28-30 footer can easisly be found for that budget. Since you want a boat that can be competively raced, I'd look at boats like the J30, Cal 9.2 and Pearson Flyer. You can even find a decent Tartan 10 for under $20K.
I wouldn't consider a 24-26 foot boat. Too small for what you describe.