While registering domain and buying the hosting provide the email ID of your client to the Registrar and Host - we mean the profiles at both the places should have his email ID. That will solve your issue.
I agree this would be the best thing to do. I’m sure many companies will pay you an affiliate commission if you join their program and let them know you are referring someone before they buy the hosting.
Or you can just walk the client through the signup process with a host. All future emails will go to them; though it’s worth adding your name as a technical contact so that you are authorized to speak with the hosting provider if/when there are technical issues.
I think become a reseller would be a great advantage. If you look around you can find some service that provides free supports for your customers, and your customers can manage their plans automatically, you can also earn money from reselling domain and hosting to new customers only doing marketing jobs this is a deal
If you don’t want to become a reseller, then that’s that. Perhaps you can partner with a hosting company (maybe a local chap?). You give him your customers to host, he gives you a part of the income. Both (actually all 3) parties win.
You should know that there are reseller hosting accounts out there that come with end user support.
There are also reseller programs, which may be more to your liking. Godaddy and Resellerspanel would be 2 companies that compete in this area.