He's also got the outboard that he was using on it - a 2006 4 horse 4 stroke that he'll add on for $800. I feel like that sort of engine would really only be useful for entering and exiting a marina, not for helping out if I get caught by weather or some other emergency OSM.... As noted, it's already on the high side for that boat, and if there are too many add-ons it'll push it out of my ball-park.
Not having seen the boat, I think the package price is higher than I would pay for a 35 yr old San Juan 24. I didn't realize the outboard motor was not included. $4800 for boat & motor, add at least $1500-2000 for a road-worthy trailer, $700 for hauling & bottom paint.... You are likely in for seven grand before you sail it. You can do far, far better for that kind of money.
BTW, a 4hp should push the SJ24 to hull speed in normal conditions. While it won't drive the boat into 10' breaking waves and an F8 gale ... well, the outboard's HP rating is the least of your problems if you find yourself facing those conditions.
My personal attitude is we should never
think of a marine engine, especially an outboard, as a lifesaving device. Their performance limitations and unreliability make them an untrustworthy crutch. Also, the narrow stern on the SJ21 and 24 means they really don't like weight back there -- wrecks speed and handling. That's a major reason we use a trolling motor on our 21.