Sahil Lavingia takes a contrarian view to the standard focus on building something that's capable of making money. Instead, he suggests, focus on building lots of fun weekend projects, and see which one sticks.
A common [negative feedback] is that you should be building a business. Worrying about money. Changing the world. David Heinemeier Hansson of 37Signals is known for lambasting businesses that seem oblivious to the concept of profitability. I don’t really agree with him. I think that you should spend time doing fun little projects. Many fun little projects. Recognize that most of them will die, but that one or two may do well.
I don't quite disagree with this point. These days, technology enables us to build projects so cheaply that "throw many things onto the wall and see what sticks" is a good selection technique. However, there's no reason to ignore the financial possibilities before deciding what to throw on the wall. If you have two ideas you feel like working on, one of which has a monetisation path, and the other one of which does not, then try the first one first, surely.