I'm not the best person to give you an opinion at all (because I've never owned this Gen of Celica). But what I have heard, these are great cars. Only common issue has to do with the variable valve timing on these engines - a cam chain lift system sometimes comes apart because the bolts holding a couple of shafts were too brittle and can easily break, especially if the engine has ever been run up at or over its red line. Other than that, I've heard these are very good cars.
You might want to ask the same question in the forum at
www.celicatech.com; this is also a great forum with a lot of knowledgeable people there. They also have a sub forum dedicated to each individual generation of Celica, so you could look at threads that pertain to this 2000 model Celica and see what the issues generally all are.
PS: Mileage isn't listed, and no real mention of any optional equipment. You will want to know that. Then check kbb.com, edmunds.com, and nada.com for the typical value of such cars with that equipment and mileage, to make sure the price being asked is reasonable, or at least to make sure you don't offer far more than what the car is worth.