I'd say about 5 million; you can safely remove about 3.5% from a trust per year through all market condidtions, and that would leave you about 175K / year, minus taxes which could be as low as 18%-20% if your structure the funds properly and only take out long term or very long term stock assets; plus there's bonds. That'll put you in the top couple of percent of income earners, and let you stay there forever (assuming you leave some in, so you can increase the withdrawl to adjust for inflation).