*I will not promote* What comes after the ideation phase for a B2B SaaS startup?

\*I will not promote" Let's say I've noticed a big pain point or opportunity in a specific sector. Afterwards, I come up with an idea of a software solution to address that issue or opportunity. I then reach out to professionals in the industry, and I receive positive feedback for the idea. Not only from multiple professionals, I also receive validation from learning about company/government incentives that are encouraging solutions that are similar to my idea. My team and I are currently developing a proof of concept (PoC) with the resources that we have available as college students. I reached out to a friend and he told me I should start reaching out to companies to procure LOIs, or even preorders if possible. But I'm not sure how to do that, especially since we don't even have an official company set up or a PoC. I think procuring LOIs is great, and when we approach investors down the line, they can definitely boost our pitch. But I'm not sure whether I should wait until the PoC is developed or we register a company. I'm confused on the path forward, is it PoC -> LOI -> spend money on registering a company? PoC and register company -> LOI? POC, LOI -> register? Or all together? I think LOI/pre-orders are the greatest validation. Last thing I want is to spend several months on developing a PoC only to find out clients aren't willing to pay for the product. Similarly, last thing I want is paying for registering a company and developing a website only to find out that our software program is not viable. But also if I don't have a PoC or a company (or company website), how do I procure LOIs/pre-orders? Why would a company care to sign an LOI or a pre-sales order with a bunch of college students who don't have a PoC nor a company?