All you are looking for for care is that he rinsed it off most of the time when he was finished sailing. Especially in salt water, leaving dirty water on the hull can, over time, weaken the laminate.
As for storage, you want to hear that either he always kept it upside down on some sort of blocks or rails (unlikely since you have to destep the mast), or that it was supported by the gunwale. Likewise, you want to hear that it was transported either upside down on a rack or platform, or that it was supported by the gunwale. The gunwale (pronounced "gunnel"). is the lip that sticks out at the edte where the hull and deck meet. It is the thickst part of the boat by a factor of at least two, so it's very stiff. It also doesn't touch the water much when you're sailing, so if it was soft, it wouldn't matter much. Laser specific trailers have no boards for anything to sit on. Instead, they have vertical supports at the edge that go under the gunwale, so the whole boat is suspended.
You definitely don't want to hear that it just sat on the ground. Not only does this put constant pressure on the hull, but the grand is wet as often as not, and dirty. So it's a constant source of moisture to work into the laminate and soften it.
To test for softness, just flip the boat on it's side or over, and pound all over the hull with the heel of your palm. There should be very few places where it doesn't hurt to do so, and likewise, few places where it caves in.
Most rigs are fine. You want to look at every opening in the mast, and make sure no hardware has ever been ripped out. There should be no distortions or tears, and any opening should be clean. If some are not, you want to figure out what it's going to take to repair it before making an offer or a decision.
Note that some boats are not trapeze rigged either. This is very easy & cheap to add, probably less than $100 for the whole deal, so don't worry about that.
The alternative is a turtle bag. It's much harder to learn how to use. It's much more prone to dunking the sail in the water, which is a huge mess. And even if you don't, it's prone to filling the cockpit with sail everywhere before you get efficient at putting it away as you bring it down. This is why it took me three years to learn how to use the spinnaker - although if I'd had someone experienced with this system, maybe that wouldn't have happened. But in any case, it's nearly impossible to do while soloing.
I have built a prototype deck-mounted spinnaker launching sock. It is functionally equivalent to the launch tube, and costs around $50 to build. It does not require any permanent changes to your boat. Some racers speculate that it disrupts airflow over the deck to the jib, making the boat slower. Others speculate that since it weighs less than the tube, it makes the boat faster. Your mileage may very. Nobody doubts that it makes the spinnaker easier to learn than the turtle bag.
I am currently experimenting with a third option - a spinnaker sock. This is a fabric "tube" that you lay on the deck, and attach to the bow. You use it like a tube, with a continuous halyard/retreival line. The hope is that it will work just as well as a built-in tube, and be way cheaper (like around $70). There is concern that the wind disruption on the deck will make it ineffective for racing, or that the spinnaker won't stow into it smoothly. Email me if you want to know how it's workign out.
It's normal for the bottom front corner of the rudder to be scratched & gouged. It's also pretty common for the dagger board to have gouges in the upper middle of the trailing edge, this is from hitting rocks at speed. If the foil has this, it's worth flipping the boat & checking to make sure the bottom back of the dagger case isn't damaged; it's usually not, that part of the boat is very rugged.
Ideally a trailer should be the gunale supporting kind described earlier. If it is not, you need to *always* destep, and flip the boat over, to put the deck on the platform, instead of the hull.
Aluminum trailers are much lighter, and therefore easier to move around by hand. With a light-gradient launch ramp, you could launch by hand from an aluminum gunwale supporting traier. These cost about $700 new. A used galvanized standard (platform) trailer goes for about $150. Plan this into your priceing accordingly. Aluminum dollies go for around $350 new.
So, you shouldn't have any trouble finding an old spinnaker rigged boat in moderately good shape for $1400-$1600. If it comes with a trailer and/or dolly, it might be around $1800-$2000. If it's not even spinnake rigged yet, you probably don't want to pay over $600. If you want a boat with a tube, they tend to be much newer. Because of thaty, they're usually in very good to excellent shape, and this all makes them more expensive. $2500-$3000 for a tube boat with a trailer is about right. You may see boats going for much more than that. Keep an eye on them, they'll probably come down.