I invite you to a dedicated Google Chat channel for all communication for the duration of the project.
I share all project update using a Kanban board. It will look something like this. At the end of each week, I send short email going over what I worked on and what I am working on next.
I share a Google Drive folder for each project. This is used to organize and share all of the assets for the project.
I share all design mockups using a tool called MarkUp. You can leave all comments and ideas directly on the design doc.
To submit a new project or feature, simply fill out this form. I'll add it to our project board and prioritize it accordingly.
I use Wave Apps to invoice directly. You'll receive an email with the PDF invoice that is linked to the ability to pay by credit card or even ACH.