@csaba I think it can be done, indeed.

However, there would be as many questions as you want. For example:

1. What platform do you use make the sell? Do you use any at all?
2. Do you use PayPal or any other payment service of its kind? Maybe a bank provided payment gateway? Bank transfers, etc.
3. Are you really thinking on a fully automated process (as complex as your answers to point 2 be), or do you need human interaction between the payment and the b2evolution cloning script launch?
4. Do you want a vanilla b2evolution site? How many collections? With or without demo content? Any pre-loaded skin?

Please provide us with more details of what you want in order to be able to offer you further help.

Regards!

This request is basically about setting up a hosting company.

For auto install of b2evolution in a hosting environment, the best solution for the past couple of years has been Softaculous: https://www.softaculous.com/softaculous/apps