How do I put this?

[iGirls]

I've got some ranks on my Forum.
For example, one called "VIP"
I would like some kind of service, so it would add them automatically.
Is that possible?

Using MyBB.

It has to be purchased using money.

I am currently using a Donate button and have to approve all manually.

[MattR]

You can use the promotions feature to move people to a new group when they reach a certain post count, rep level or time registered, if that's what you mean.

[iGirls]

A sorry.
Lack of information.
It has to be purchased using money.

I am currently using a Donate button and have to approve all manually.

[Dillon]

Oh! There's a plugin for that in MyBB Central. But you have to pay for subscription.

[Jordan L.]

It's called MyIPN Paypal Subscription, a plugin that Omniscient himself made. It's very nice and easy to use. You must be a paid subscriber to download any of his plugin.

[DAMINK™]

Yep its a solid plugin to be sure.