Japanese cars tend to hold their value very well, but you should be able to find a decent car in that range.
If you are not an experienced used-car buyer, by all means find someone who is to come with you, and also be prepared to have a trusted mechanic look the car over. No bargain to find that your new purchase won't pass inspection without a thousand bucks worth of repairs!
General principals- look for bare-bones models without a lot of special features, add-ons, and so forth. Keep it simple. Expect pretty high mileage in this price range, but don't worry, a lot of these little guys go well over 200,000 miles without major problems.
See if the guy has maintenance/service records. See what parts have been replaced. At 100,000 miles, you'd expect wear items like brakes, tires, exhaust, etc may (or should have) been replaced.
Take down the VIN and think about paying to run it through one of the online services that will check for repairs, recalls, and so forth.
Good luck!