Offhand I'm not really a fan of Catalinas...
That said, there's a Catalina 30 for sale here for not very much so I took a look at the sail plan and accommodation layout and it's really not a bad boat.
A rather nice boat actually...
From what I gather the boat sails well and it's an active class so you'd hear any issues in terms of performance or construction and no one seem to find fault... A good sign.
As far as construction goes there are some built in issues but no biggie and it's important to keep in mind that ALL BOATS HAVE ISSUES and it is fairly simple these days to find out what they are by checking out the boat's user group. In the case of the C30 the only things that jumps out is thru-hulls.
Doing a quick price check in the usual places the going asking price for an older C30 in good shape is around $10K (+/- 20%). Definitely VolkCruiser material.
It would be to your benefit to keep in mind that with good examples of the C30 being not very expensive that means fixer-uppers should only be considered if they are seriously rock bottom cheap.
You can find a lot more info on the design at the Catalina 30 page which you might want to check out..