- Can you set it up so you have a one time sign up fee, and then have
a recurring charge as well? Does this depend on the payment gateway? Does authorize.net support this?
Yes: http://drupal.org/project/uc_recurring
- Can I automatically create a user and log them in before I redirect
them to the checkout page? I would be doing this in a custom module (basically a landing page with contact info)
Not sure what you are asking. If it's a custom module, then you can do what you want. But I think Ubercart can do this natively. And of course it anyway collects contact info.
- Can i take some fields that I'm getting from a landing page form
(custom module's form) and put them in ubercart for the billing address of the user i just logged in (above #1) so it is prepopulated at the checkout page?
Don't think so. But why not just use Ubercart's address data?
F