Why do you think you have to lose money to attempt to build a side project? I built one in my spare time over about a month, with a specific niche market in mi

Why do you think you have to lose money to attempt to build a side project? I built one in my spare time over about a month, with a specific niche market in mind, and my first customer ready to purchase. It was profitable, not counting my lost leisure time, from day 1. A few years in it's not made a ton of money, but it's still profitable every single month without fail, because even one customer will maintain that. I have not touched a line of code in ~18 months. "They didn't come" to my project, either. The niche needs non-adsense sales, and my partner failed me on that front. Still, I didn't spend a dime.