This was my response to the above question on Quora
The only way to make money as an investor in startups is to have a portfolio of investments. If you invest only in one and hope that it works out well, well, the chance are rather slim.
Startups by design are experiments … a set of assumptions that are being tested in the market by someone who has the conviction about a concept. Sometimes the experiment works, often it does not. But that is the only way new ventures get created… by testing many ideas.
So, if you want to make money by being an investor in startups, think of investing (or better co-investing with other angel investors) in 15–20 startups over a 3–4 year period. Some of the companies you invest in will shut down. Some will struggle to keep afloat, but will amble along. Some will become good businesses for the entrepreneur, but will not give any return (exit) to investors. Only a very few of these investments will give multi-bagger returns making up for the losses incurred in those who did not do well in the market.