_Users can buy subscriptions (for another site, no relation to CB Subs) for 5 Euro per subscription
No idea how you plan on interfacing with the other site so I can't say yes or no to this question. If you just need to for example add something to an external database table you can use CBSubs SQL Actions or CB Auto Actions to push data to another database based off subscription state.
_They need to input the number of subscriptions that they want to buy
Create an integer field for them to fill out during registration. Next create a new promotion in CBSubs Promotions that always applies to your plan. Then use the following settings in your promotion to increase the price of the plan based off the number they put in that integer field.
The promotion is: A fixed amount
Fixed Discount Amount in currency above: -[FIELD_NAME]0
The above would increase the price by $10 per site. If you need more complicated calculations you'll need to use CB Code Field and a Code field to use PHP functions to calculate your price. You'd then just substitute that into your promotion as follows.
Fixed Discount Amount in currency above: -[FIELD_NAME]
Example code field usage as follows for $5 per site.
Code:
return ( (int) '[FIELD_NAME]' * 5 );
_The user gets a detailed invoice where he sees how much tax he has paid AND how many subscriptions he has bought.
CBSubs already handles properly providing an invoice. As for also having it show how many sites they subscribed for you can add your integer field to "Payment item text" under the Pricing tab of your plan so that detail is also added to the invoice item.
_Recurring either per month or per year.
CBSubs supports monthly and yearly recurring durations, but if you want to support both you'll need 2 separate plans for that.
You should be able to give all of this a try on our demo site below excluding the code field usage.
demo.cbdemosites.com/
krileon
