I'd like to echo the caution to make sure that the model you're getting isn't involved with any recalls.
Also, please check to see what that seller's other items are. If they're selling lots of strollers, there is a possibility that they may not be selling personal strollers that their children may have outgrown, but ones that are acquired through less conventional means. They may be getting them perfectly legitably, but...my niece in Texas had a friend who was getting a stroller sent from ebay. Instead of a stroller delivery, she wound up having police come by to get her statement after telling her that the seller had a local theme park annual pass, and was apparently going into the park once a week carrying her toddler and pushing the child out in a nice stroller later in the day.