I disagree with the generally accepted one- build something you want. This is a fine thing to do but the overwhelming majority of good software business ideas aren't for consumers or developers. The overwhelming majority of workers who have problems that could be fixed by software are not developers. Lots of opportunities out there...
Building something you want usually means that you have a deeper understanding of the problem. Also, chances are, that you are familiar with the market, alternative tools, etc. Which is a must for creating a good product. Actually wanting to use it adds a little bit of passion which definitely counts in the early stage.
clearly there are advantages if such an opportunity presents itself. Of course if you are a programming by trade, chances are it will present to a lot of your peers as well
