Answer by taking a quote from the following article:

Scott W. Rothstein (born June 10, 1962) is a disbarred lawyer and the former managing shareholder, chairman, and chief executive officer of the now-defunct Rothstein Rosenfeldt Adler law firm. He was accused of funding his philanthropy, political contributions, law firm salaries, and an extravagant lifestyle with a $1.2 billion Ponzi scheme, one of the largest such in history. On December 1, 2009, Rothstein turned himself in to authorities and was subsequently arrested on charges related to the Racketeer Influenced and Corrupt Organizations Act (RICO). Although his arraignment plea was not guilty, Rothstein cooperated with the Government and reversed his plea to guilty of five federal crimes on January 27, 2010.

The allegations are: George Levin was the general partner ("GP") who solicited each limited partner ("LP") to contribute at least $1 million. Initially, each LP contributed $250,000, subject to periodic capital calls up to the amount of their commitments. They were promised 12% annually (15% for first $100 million), to be paid quarterly. The general partner had to maintain a balance of not less than 10% of all contributions after any quarterly distributions. The general partner also gave a "clawback" guaranty to all LP's equal to their original contributions. LP's could not request redemptions during an initial one-year "lock-up" period and were required to give 90 days' notice for any withdrawals. Redemptions would be paid from the GP's own capital account "to the extent available" with a 10% hold-back, but otherwise, only from the purchased lawsuits settlement stream.  Banyon had paid Rothstein's firm at least $656 million, but the law firm anticipated $1.1 billion over a maximum 24-month period. It allegedly received and reinvested about $500 million. Levin expected to make 40% over 24 months but to only pay out 24%. Rothstein's law firm's IOLTA trust accounts established "for the plaintiff" in the purported litigation settlements were used to fund the phony settlement accounts, after the law firm had paid its overhead, keeping its insolvent operation afloat, which included "gifts" to partners and money given to politicians, charities, and pay for a massive advertising budget, as well as Rothstein's personal lifestyle, over three years, amounting to approximately a $500 million loss.  The interest on the funded IOLTA accounts went to the Florida Bar monthly, which was many millions, based on the Banyon contributions. In its prospectus, Banyon claimed to have a legal opinion that Banyon's interest in the IOLTA trust accounts "perfected automatically on execution of the transfer documents" - that the lawsuit proceeds assignments created by general counsel, David Boden. The LP's were warned that they could be taxed on the Partnership's income and realized gains even if no distributions were made. As long as reinvestments were ongoing, the ponzi scheme was facilitated.

what was their income strategy?
They were promised 12% annually (15% for first $100 million), to be paid quarterly.