A good way to start is to look around for things that people or companies are already using (some B2B software tool), and see if there are a ton of people compl

A good way to start is to look around for things that people or companies are already using (some B2B software tool), and see if there are a ton of people complaining about it (maybe some bad feature, aggressive pricing model, customer support etc.). If so then you can start building an open-source version of it, since you already know what are the key features to build and add.