Yes. Here’s why…
You get requirements from your daytime job.
This is so important that when I stopped moonlighting and went full time on my start-up, I kept an outside client 2 days per week. Let me explain…
One of my biggest problems has always been WHAT to build, not HOW to build it. Many successful start-ups have been the result of building what one needed oneself. I just expand “oneself” to include my parttime clients. Think you have needs? Wait til you see the long lists of needs in almost any small business. Sure, I lose a little time in the development cycle, but I more than make up for it at user acceptance time. No cycles there - I already know what they want.