[Steve Carlton]

First thing I would say is benchmark the value of the used one by figuring out what a new one would run, especially if you wind up with a 2 year old one. Look at TRUECar, Costco, and CarGurus, as well as other sources. My thought is to make sure you save a sufficient amount to justify used vs new. If a new one isn't that much more and you get a great deal, consider you'll have the extra 2 years of life in the car and a fresh start with new tires, brakes, and service.

I'd recommend getting a CPO from a Toyota dealer. If I'm not mistaken, it doesn't cost them much to make a car a CPO and you're a lot more likely to avoid getting a rat from a non-Toyota dealer. There might be a preferred APR on a CPO, if you're financing. Either way, I'd do a PPI at a dealer.

I don't think there's a rule of thumb on wiggle room. You won't know how aggressively the car is priced. Maybe the dealer has had it in stock for 70 days and wants to blow it out and prices it accordingly. No wiggle room in a case like that. Get a feel for what they go for compared to kbb.com and you'll know a good deal when you see it or where the price needs to go if you need to negotiate. A dealer should have a link to a Carfax. It may not have all the info, but chances are good what's on there is accurate. Depending on where it was serviced, the service history could be on there, or it may have been well serviced and you can't see any of it on the Carfax.

A private party purchase should be okay. You're more likely to know the service history, get a feel for the owner, and probably get a better deal, too.