Domain wise Godaddy is very good. Great prices and additional discounts when you get the reseller account.
Hosting wise... you really need to go with dedicated or at least VPS if you have sites that need 99.99% availability. "Anything else is a second hand" but to me dreamhost is the hosting of choice when it comes to shared hosing.
If you want to resell for a company, be their customer first. Sign up for a standard hosting account, host your not-so-essential site on it and see what your experience is in terms of uptime, speed and support level is. If you are satisfied with what you get after 90 days, you can consider reselling for them. The good thing about reselling is that you do not need to worry about the technical aspects of the hosting but then the bad thing about reselling is that you need to depend exclusively on the web host for all technical aspects. If they are bad, they will make you look bad. In Godaddy context, reselling using their Wild West Domains program find out if you are providing the technical support for your clients or GoDaddy is.