I had a 19 husky. One of my favorite chassis ever. Same chassis as my wife's 2021 FC250.
That bike is a 450SX. So narrow ratio 5 speed. Smallish tank, no kickstand, 19" rear wheel. And they definitely rode it in the sand. If you want an SX it's not a bad deal for what it is. You can make it more off-road friendly (see my wife bike thread for mods)
It looks like it has AEO aftermarket suspension valving (I like their stuff, I have it on one of my bikes) ask what weight and skill level it's been valved for.
Pop off the side plate and look for sand or dust under the air filter and that the air filter is sticky and not dry.
Tap the handlebars softly on a stand to see if it needs headset bearings.
Lift up and rear wheel on the stand and listen for knocking to make sure it doesn't need linkage or swingarm bearings.
Rock the wheels left and right to check wheel bearings.
Check brake pads and rotors for scoring.
Get it hot and then see if it still starts easily. If it starts poorly hot, that's a sure sign it needs a valve adjustment then replacement soonish. A top end with piston and valves is about $2k in parts.
Let her rip! 🤞