Yes, anyone can apply. But it's important to refrain from over engineering how it's built, what framework or what model. These are all secondary for a startup.
MVP matters.
Customer traction outweighs all.
Getting folks to pay for AI is challenging. If you manage to crack a niche and do so and pay or pre-order - that will give you an understanding and core tenant that is expected from companies to scale once they get accepted into YC.
It's tougher to get the average chatgpt free user - to pay for an unknown startup. All you need is one company to agree to pay. Because if you can get 1 (not friends & family), you get 10. And then get 100.
If I were you, my #1 focus for the entire team would be to get 1 company to pay, before starting to build or touch code. Get the initial NO's to tweak every cold call/email/pitch refining every day until you crack your first deal. I would stay away from long tail consumers.
Good Luck!