Setting up Business Accounts as a payment method

[ivanpope]

I want to be able to set up Accounts for businesses who want to buy from me and be invoiced (rather than pay on the spot).
I can't work out how to approach this - i.e. is it a module thing (is there a payment module that does this) or is there a way to set it up, maybe with Groups or something?
What would happen:
1. Business would register at my shop and then request account.
2. I research business and decide whether or not to open account
3. Once account is granted, when they come back to order they choose 'Account' as payment type.
4. Purchases are despatched and outstanding amounts are invoiced by me (manually?) at the end of each month.

I'd love a module that handles all of this including the invoicing, but I'm happy to handle it manually for now.

Thanks for any thoughts or pointers.