Typically the way it works, the higher up the server chain you go (example from shared to dedicated), the more responsible you become for maintaining the server.
In regards to a dedicated and backups, for the most part you will be responsible. The vendor may have some sort of rotating backup for a couple of days, but they are not going to hold backups weeks on end, and most likely are going to charge you a restore fee.
In regards to hosting and what server you should be on, it really depends where you are trying to take this. Honestly, if you are going to be selling the hosting as a secondary service, I would stay on the reseller. The reason for that is because it is on a resellers, you really don't need to worry about troubleshooting and maintaining software. You can more or less hand that off to the vendor.
You will see on a dedicated the cost per gb is much lower, but you have to factor in the point that you need to manage that entire server, which is going to cost you time, which costs you money.