My mtb is a used Titus Racer X I bought on ebay. I never could have afforded an equivalent bike if I'd gone with a new one. That said, I did have to change out several of the components that were worn and/or did not work for me, but still, the cost was much less than buying new, and I got great "bones" to work with. I did know what size I needed going in, as I had a much less expensive REI Novara hardtail that fit me great, and I picked the Titus size that was virtually identical in geometry. Knowing your geometry requirements is crucial if you can't test ride the exact bike you're buying used.