8
You could use one of the advance contact us modules which allows you create many custom fields.
Then on submission you can state, that you will be in contact within X amount of time and will arrange payment, etc, etc.
Is there a real need for a customer to register on your web site?
If so they could register then you direct them to this section where they fill in a form for a hosting plan.
Just another idea of course, not sure how much help it is, lol.
You could also install calander module for use by only yourself, which will have the dates of renewal in, along with a block only you can see which will list up and comming dates, this should then remind you to E-mail an invoice out.
As a self-employed businessman, I know that invoices are easy to create, you dont need any fancy software for this.