It's certainly light enuf to trailer, tho loading and launching won't be too fun unless you have access to a hoist. The SJ24 was one of the racier Clark designs, meant to compete with the J/24 as a price-point OD or club racer. It is nowhere close to the J/24 in speed, however (219 vs 168). Its rig is undersized, it won't hold with the J upwind a'tall, and you hadn't ought to make up time on the downwind leg or you'll be washing your Windex. A few people still race them, and they can do well under PHRF with a good crew.
The boat's most famous quality is its white-knuckle ride under spinnaker. It rolls like a ferry. You'll be glad for the small cockpit when lying on your side. But if your throttle back or sail wing-and-wing, it will behave fine. Many of the Clark boats feel
faster than they objectively are -- quick, rather than fast -- which makes them really nice daysailers, if you don't have any particular place to go.
You can singlehand the boat fine. Loads are reasonable and everything can be handled at the coamings or coachroof. (You will love the roller furling.) Build quality was 'meh.' General glass work was about standard, balsa decks on all Clark boats seem to suffer water intrusion. Look for soft spots, maybe use that to negotiate.
Stock deck hardware was not great; bonus points if that's been upgraded to Harken or similar. (From the ad, looks like lots of fresh Schaeffer gear -- that's good.) Sails are cheap for this boat; you should be able to find good used rags all over the PNW. Most parts still available & what isn't can be substituted or fabricated. It's a cheap boat to own & lots of fun to sail, tho I'd want some experience & a beefy helper before taking it out in a blow. Not a boat for the open ocean, but good fun/$ ratio inshore. If it checks out, go for it! (Then take that bloody danforth off the bow pulpit....)