Need help to make this a PAID Forum

You could do most, if not all of this, using a subscription plugin.

Let's start with the free trial members.

First of all, MyBB has a "group promotion" feature - I assume SMF has something similar, though I've never used it so you may need a plugin for this too. Essentially, members are placed into a default usergroup when they register (in this case, the "free trial" usergroup), and can be set to automatically be "promoted" to a different usergroup after they've been registered for a certain amount of time (a "non-client" usergroup who does not have access to the forums).

Then with a subscription plugin, you'd be able to create a special usergroup (a "client" usergroup) that users are moved to once they pay. This usergroup would have full access to the forums (until their subscription runs out, if you're charging a monthly/yearly fee).

I'm not sure of how you would differentiate between forum only clients and existing clients to another product - honestly you'd probably need to hire someone to custom code this.

I have done this before with SMF, as said above you just need to use the subscription feature in SMF (its built in). Make a new group and change the forum permissions so only people who have paid can see the paid forums. You can easily have different price levels by simply creating more groups for each level and changing the permissions based on your needs.

Hey guy's

many thanks for those tips, I will take a look into this asap.

Would be great if I can resolve this over a simple plugin.

G.