They are asked to give £3,000 to a a network member (family member or friend in most cases). their return as a new investor is expected to be anything up to £24,000, as hierarchy or the system works its way along.
Success depends on new investors being introduced. However, bu invariably it breaks down as the contacts dimish and the £3,000 investments stop. As a result, those joining the business later along the line not only would lose any gain but their original contribution.
Many claim to have made large amounts of money from schemes like this, and probably have but that if far outweighed by the thousands more who joined the scheme and lost money.