I want to mention one point essential in the reselling plans as well as in shared hosting, I mean CPU increase, usually reselling/shared plans have enough disk space and bandwidth, it's CPU limit that makes sites upgrade to vps.
And I recommend to get a reselling hosting provider who allows for the CPU level increase in their reselling plans, they track the total CPU level committed to each server and increase it when it's necessary. I know this feature is enabled in Utropicmedia.net reselling plans, there should be other providers allowing it.