I've always wanted this. Full time jobs like this are called async jobs. Isn't gitlabs like this

Contracts are harder because everyone wants a call to form some relationship. I try to push my contracts into a different relationship as time goes along like this because it is so much easier and calls get longer.

My method is to have a separate line item on the invoice for calls and no lineitem for email. The 4 hour calls quickly dryup when someone is being billed.

On upwork you can find a lot of projects without that requirement.

Get good at finding clients without talking to people. Filter out those that want phone support.

In the end you might just want to start a pure online business.