Recovery questions have been phased out as a security measure by Jagex a while back. Also, even if you're given access to all correct recovery information by a seller, it's entirely possible that they (the original owner) will still be able to recover it and/or that your own recovery attempts will be denied. For that reason, the most important thing to do is to purchase from a trustworthy seller, and, in my opinion, rather than asking for account details, just stay in contact with the seller so that they can help you sort out any future account issues.