First, get a copy of Don Casey's book "Complete Illustrated Sailboat Maintenance Manual". In it he shows how to do your own preliminary survey. It is worth its weight in gold. It is an expensive and heavy book. Probably around $100 + taxes.
Second, if you are still interested in buying the boat, contact your boat insurance broker for a list of approved surveyors in our area. Then get a full purchase survey. You will need it to get insurance and you will need a minimum of two million liability insurance to get into a marina. probably around $400-500 plus a half lift at about $200 + taxes.
Third, if the sailboat does not come with an assumable moorage contract, go to all the marinas in our area to see if they have moorage available and put your name on all of the wait lists. It may cost a couple of hundred to be on the wait list. Annual moorage is about $4,000 to $5,000 + taxes per year for a nominal 27 foot boat. Your insurance will be around $500 per year and you will need to spend an average of around $2,000 per year for normal maintenance such as bottom paint every second year and minor repairs, plus any major repairs and upgrades.
Fourth, if you think this is expensive, you should not get a boat. A 27 foot Catalina of that vintage typically has an outboard and should have a buy price of around $10,000 +/- $3,000 depending on condition.
Finally, if you get the sailboat, welcome to the best sailing area in the world.