Ask HN: How do I come up with monetizable SaaS side project ideas?

Hello everyone, I'm a software developer with an year under my belt. I have been doing some freelance work like developing websites and making react native apps for small businesses owned by my friends. I do love the gigs, but I want to build a Saas that will generate some passive income. I have a couple of ideas but they can only be monetised through ads which is a big no for me. Can you help me find some ideas or some inspiration for a good side project? Thanks in advance.