Hi Mayki , yes, I tried this, but I needed something else. So I finally solved it in another way:

• Since I use a custom module for my paid levels, I can use the regular Paid Levels separately.
• Now new users get a special "Beginner" level with very restricted access.
• On the home page I placed the Paid Levels block. There is only one plan to choose: 30 days for free. The "Beginners" only see this offer, nothing else.
• On the other hand, no one else sees this offer, because I blocked it for all other levels. 
• So after a Beginner chooses the free level, they have full access for 30 days. After that they have to use my custom module.

I implemented this yesterday and it seems to work. 😎