You ever drive a 2 wheel drive s10? There's a reason 4wd is an option, 2wd is goddam useless in these things. I got mine stuck in my front yard, my perfectly level front yard, because it rained a little bit and the grass got wet. When it rains I can't make a complete stop at an uphill intersection because i'll never get it moving in the right direction once it loses all its momentum. People always talk about s10's spinning the tires so good, like it's a measure of power. It's not really anything to do with the power, the 80 horsepower 4 cylinders still spin uncontrollably. They're just designed with all the weight over that front axle and nothing to keep the rear tires hooked up.
But a 99 4x4 for 4,200 sounds like a great deal. There sure weren't any deals like that around when I bought mine. $4,100 bought me a 93 extended cab with 93,000 miles, 2 wheel drive, and bad engine mounts (found that out 2 days later when the fan started hitting the shroud). Prices around here suck though.