2 contents, 1 for visitors and 1 for specific group

I could use some advice for a realization of a page that has the following characteristics:

– Visitors X come and see a content (in practice are encouraged to ask for a license)
– Users Y (one specific group) can see the true content within page for visitors

Do you have any advice for me? Plugins, html code or other solutions which are less invasive as possible?

[No bumping. If it’s that urgent, consider hiring someone.]