It's not exactly passive, but real-estate is where you want to go for a reliable, substantial, secondary income stream. Obviously, if you are in an insane market, it's difficult to get your foot in the door, but there are some options. One can typically get an FHA loan for multi-family properties of four units or less, if you are going to be occupying one of the units, which allows you to get in the substantially lower down-payment. Renting the other units will cover the bulk of the mortgage, and you also have a roof over your own head, and you should have enough slack to make extra payments. PMI is kind of a pain, but unless things do go over a cliff, within a couple of years you can build enough equity, and valuations will go up enough that you can refinance out of FHA.