Shape of the organization alone has no bearing upon legality or illegality. These plans usually show that if you sign up to be a distributor, you will receive commissions - not only on your sales of the plan's goods or services, but also on the sales of the people you recruit to join the distributors. Pyramid schemes have a similar structure, but a completely different focus. They concentrate on the commissions you could earn just for recruiting new distributors, and generally ignore the marketing and selling of products or services.
Most countries outlaw pyramiding.
It is illegal to pay for simply signing others up. These plans can collapse quickly - and also may be illegal pyramids in disguise. Any legitimate business is going to cost something to start. No one can guarantee your downline business growth - ever. Again, it is your efforts that will cause this to happen or not happen - no other guarantees should be respected.