Before you start looking for bikes online, you need to find out what size bike fits you and then look for that size. If you purchse a bike that is not the right size, it will most likely not be comfortable which means that you probably won't ride it. If it is the right size bike, you will want to test ride it a couple of miles to make sure that it is right for you and meets your expectations in handling and ride quality, sort of like a test drive when you are buying a car.
As for the Scott Speedster, here is a link with the particulars of the bike. bikepedia.comBikeSpecs.aspxOpen ↗
Brand new, this bike retailed for $700. Like a car, most bikes lose a good percentage of their value once they leave the bike shop. If the owner did several upgrades in components or added a bunch of stuff, it may be worth $500. If it is in very good condition, I would probably go for it as long as it was the right size and I enjoyed the test ride. Just remember, this bike is no longer under warranty and you are getting it from someone who wants to get rid of it and is not worried about customer satisfaction or follow-on business. If I were in the market right now, I would save for another month or so and then go to my LBS and see what they could do for me.
