Usually, if you run multiple startups it is a clear signal that you are not committed to any of them, and is not going to look good for you. However, one reason to have multiple things going on, typically, is if you have a consulting company that is paying the bills necessary to launch your startup. Eventually, you will end up winding it down to focus on the startup full time, but if that's how you get the company off the ground, then it's a valid reason to have multiple businesses going on simultaneously.