If it attracts your attention sounds like it will be a fun boat.
On any daysailer that is 25 years old, you should expect
- old sails (need too be replace - this is the boat's power source),
- aged rigging (another consumable),
- possible blemishes on the deck/hull (inspect for water intrusion - repair issue),
- hardware that my not have been serviced (inspect, repair/replace).
John Kretschmer described the Harbor 20, in a 2007
Sailing Magazine article, as, "a handsome daysailer ... [which] merged ease of handling, solid construction, exciting performance and traditional lines."
While you are looking at the boat's flaws, the owner is remembering all the good times and valuing the boat through rose colored experiences.
Good luck.