Unless you're thinking of riding mainly downhill trails I wouldn't get a kona stinky for general mtb use. They are great bikes and well built, but all that downhill suspension and additional frame mass is going to be a pain when pedaling on the flat and up hill. You can stiffen the suspension, making the bike more efficient for pedaling, but that sort of negates getting such a long travel bike in the first place. Saying all that, I ride a 6” travel bike almost all the time and love it. Being able to ride over almost anything is kind of fun, but my frame doesn't have the same slack geometry as a downhill bike and pedals well.
You don’t mention the age and condition of the bike, but for that price I’d be looking for a 2008, maybe 2007 model in good condition. Maybe a few signs of wear and tear, couple of scratches. Wheels need to be true, hubs tight, suspension should have been serviced at least once since new, no give in the headset, possibly a new chain and cassette. If this downhill bike had been ridden as intended as a downhill bike you’ll need to double check shocks for blown seals, rims for dents, disc brake pad wear and the frame itself for cracks. Look around the areas where seat post and top tube connect and the headset for small hairline cracks. A quick an easy test is hold the bike up, balanced on its back wheel and bounce it. A good bike doesn’t rattle.
As well as considering frame size you may need to check the coil fitted to the shock is correct for your weight. They’re pretty cheap, but something additional to add to your budget.