Buying second hand is the way really, it means you can pick up a dirt cheap bike, but it will have a super spec, and depriciate less if he decides to sell. All the Onza full builds on www.tartybikes.com and this year it looks like theyv'e got it right! The spec's are pretty good and the prices are very reasonable, however most riders, will upgrade the Onza's as they go along to make them easier to ride, and this can get pretty expensive. I would say look out on here, as some bargin bikes come up! I'll be selling my top spec KO bike for about £300 soon, but there are loads of bikes out there which will suit your grandson. I would stay away from that bike you listed. Look for a good quality frame (ie. the frames on tarty), the most durable brands are the echo, zoo, adamant, etc. With companys like koxx and monty selling light weight competition frames which genrally tend to be a bit snap happy) What size is he looking at getting a mod bike 20" or a stock bike 26" EDIT: and how much money has he got to spend?