this should be moved to Scams and Phishingand they most always are based around COMPOUND INTEREST which means the "potential" to make quick and big profit is immense but if you study the logistics of them they are totally unsustainable.
where is your interest coming from?
its coming from the poor souls who join up after you with the money they put in hoping to make just as much money as you.
this also means you are paying the interest for the guys who joined before you.
these HYIP sites dont last long, they pull the plug as soon as the scam becomes saturated and just before the house of cards implodes on itself.
you see they put in a small amount, enough to pay the initial people who join and soon when they get more members it kind of is self sufficient up to the point of the implosion leaving everyone bar the initial few high and dry.
stay well away