<prompt> Human: Hi, I was do some long-term planning, and was looking at the idea of setting up an investment account whose purpose would be to generate the income needed for cars for my wife and I for life: the idea of setting aside money now and then never having to save for a car again is appealing. Heres the basic rundown:We plan to hold onto our cars for a long time: 12-15 years buying 3-4 year old cars. With two of us, that means a car purchase about every 6-8 years. We dont need anything fancy: wed be happy over the long haul purchasing cars that cost 12-15k in todays dollars.The idea would be to set aside a chunk of money now, invest it in something like a SP 500 index fund, and then pull off the inflation-adjusted earnings to buy cars for ourselves while letting the principal continue to work to get our next car for us. Back of the envelope math seemed to indicate itd take about 40k to pull this off. So my questions are:- Has anyone else tried this approach?- Is this a reasonable idea?- Is my figure for whats needed in the right ballpark, or should I be aiming for a different number?  <response>: I think if that is a method that works for you thats great.If you qualify for low interest rates, like 2 or so, I think its better to just get an auto loan and use that to buy a car and leave your money invested. But if you dont qualify, or prefer to avoid debt then theres nothing wrong with your method. 