There are some free business models (e.g. Google, Facebook) but this is a hard route that requires tons of capital, and probably involves selling the free users as the product.
The reason I was struggling with this question was the fact that there would be no self-serve model to begin with. I would be onboarding every single customer 1:1, and then once it has been set up they can take it up from there.
It's also fine to do things that don't scale, that's how most startups launch. It might not keep up with the pace of growth, just have a backup plan for that.
Also just saw the last question. No, probably don't charge them yearly for a product that hasn't been around for a month. We see a lot of products where the site keeps breaking down after a few months. You need a lot of trust that you're willing to commit. Many get it with a 100% money back guarantee or even 110% money back.