i'm thinking about buying a 99 explorer. any reason not to. like gas milage or anything

 

If you read through the posts, you will see that electrical problems are common, especially with the windows, though I have never had any problems with the windows on my 99. The only electrical problem that I haven't been able to fix is my rear wiper..no biggie..
Expect to have the trans rebuilt between 100 and 125k miles. I have the 5.0L which runs strong even at 142k miles. No smoke or oil leaks. At the mileage that I have, plus the age, I am due for replacing the suspension (shocks..).
Other than that, the only things I have replaced were the alternator, the TPS sensor, wheel bearings and trans (under waranty).
A 1999 is 8 years old already. Any vehicle with this age will have mechanical break-downs somewhere. If this vehicle was taken care of in its past, scheduled fluid changes throughout, and you continue to keep it up to date, you should be fine. But used cars are used cars. If you are tight in your wallet, then this used truck might not be the best choice. Rebuilt trans runs @ $1300, whlle bearings run @ $700, alternator (motorcraft rebuilt) ran $270..