If you're in the USA, and you're planning to get into the USA reseller web hosting industry, you need to consider one major issue, first and foremost: would you like to offer Unix-ready features along with Microsoft-only ones?
Offering Microsoft-only services may seem to be the smart choice, but supporting Unix is its own asset, which could open a world of opportunities for you as a USA reseller web hosting outfit. In fact, if you have avenues to ask for both Microsoft and Unix support from your web host, all the better!
One downside to reselling web space instead of putting up your own server is that you don't get to control the basics. As a reseller, you may be able to change things around via the standard control panel. You may even have limited access to certain features like merchant accounts and secure site hosting. But when you want to switch between operating systems, or OS-es - it's unfortunately not your call, but your web host's.
Web hosts determine the kind of OS-es that run on their servers. Many web hosts offer both Windows and Unix features, by using Unix machines as servers, and then just running Windows programs and servers within these machines. Over time, Unix server OSes have become increasingly tolerant of Windows programs, which makes a Unix server a sweet deal for web hosts and resellers alike.
Unix servers are cost efficient because they are ideal for running open source programs. Preferring open source programs help save on operational costs, since they're mostly free for use, depending on the specifications of the persons or outfits who developed the codes to be used. When you run paid programs or servers on your machines, you don't only need to think of the cost of buying the software - you also need to consider the potential costs of license renewal.
There is, after all, no assurance that software licensing will cost the same throughout the years! And you have to consider that in your profit projections if you are running a webhost. Thankfully, you don't need to be concerned with that as a reseller. However, as a reseller, you should be aware of what software your potential customers will need.
If your web host only supports Unix and open source features, you run the risk of losing a big part of your clientele. But you run the same risk if your host only supports Microsoft and Windows! As a USA reseller web hosting outfit, you should be intimately aware of the needs of your target market.