If you build for yourself, you'll have a first customer right away. But, on a less trite note, it's highly variable. For my most recent project (sci.chat), it

If you build for yourself, you'll have a first customer right away. But, on a less trite note, it's highly variable. For my most recent project (sci.chat), it took me a total of three weeks from starting to get my first customer. They came through a reddit post. For other projects I've made, I've gotten zero customers after months of effort. In my experience, relying on organic growth instead of "going viral" attempts has worked out a lot better.