I would like to second this as great advice. I built my company exactly this way. Ended up doing something completely different than what I originally did, but that’s how it seems to go. The best way to start a business is to start one: get a customer and solve a problem for them. The best way I’ve found to get customers is to call your friends, past coworkers etc. since you’re early on, it’s harder to get strangers to trust you. I had no luck early on trying to find customers online, picking up the phone and connecting with people is the best way. I still get customers that way and do bacially no advertising or marketing.