Some cycle shops sell used gear, but I've got all my gear off of Craigslist for cheap. Both chest protectors I bought were $20, bought nearly new pairs of riding pants for $30, near new pair boots for $40 and jerseys can be had for $10-$15. As for helmets, don't F around with a sketchy used deal you know nothing about. Get something new that you can feel comfortable knowing it hasn't been crashed.