DynamicSMS is clear, simple and free to join.

Firstly you have to join, to do that click on 'Join Now'. Once you have joined:
 

You can refer people to join (who become your Tier 1 members);
Your Tier 1 members can then each refer people (who become your Tier 2 members);
Your Tier 2 members can then each refer people (who become your Tier 3 members);
Your Tier 3 members can then each refer people.
 

Advertisers are charged a fee per SMS advert we send.
From this fee, they pay you the following commissions:

5% for adverts you receive
15% for adverts sent to your Tier 1 members
7.5% for adverts sent to your Tier 2 members and
5% for adverts sent to your Tier 3 members.
 

In turn, each Tier will receive commissions on the same basis, so...
Your Tier 1 members will receive commission on their Tier 1 members (who are your Tier 2 members) and so forth..