well, you just make a note while searching for a good reseller
1)First decide which Platform you want to offer hosting upon
2)check which control panel they offer you to manage your reseller account
WHM/CPanel , DirectAdmin, were some good Linux based Reseller & Site Control Panels.
3) then, think of, how much space you feel required to start with
ingeneral, if you feel you have better budget, then start with around 2 to 4 GB reseller space, and if you think to start minimum, think of starting with 1GB reseller space, which is also SUPPORT you START better to start sufficiently good
4) then, it is reliability and other factors you have to look about, and info about the host, then DC where the servers are located in, and all about network speed and other aspects etc of the server.
5)Your budget: think of how much price you think you can afford to makea better start of your Web Hosting Business
research the hosts, you can do find info here in this forums, also through Google
see if they offer any other features which are additional and significant
these were basic steps, and ithink, you can find a BETTER Host to Support YOU start Your RESELLER Business in a more better way: