Ask HN: Is this sufficient customer validation to start coding my SaaS?

I chanced upon the idea of providing a certain brick-and-mortar vertical with the ability to provide monthly memberships a la Amazon Prime. My target customers are independent service providers of some kind whose services lend themselves easily to an in-house monthly subscription plan. Their customers already pay monthly for a plan, though not directly to them -- this is just how the industry works (sorry for being vague).

I'm offering them an SaaS platform to "Costco-ize" their business. A quick search revealed that it's a major pain point, and the solution would provide tons of benefits. Literally my target customers are blogging about the solution, but they just don't have an easy way to do it. I don't think selling my target customers would be an issue -- them selling their customers might be an issue though, as it would be a departure from the status quo for their customers.

Basically just recurring billing for XYZ vertical

While I've yet to talk to any of them yet (I literally just got the idea, I'll talk to some soon), it seems like the idea has legs. A quick search reveals a few recent startups tackling this vertical, charging good money for it ($200/mo on average).

Is it safe to start coding now?