Using vibe coding to build something to replace an enterprise SaaS offering for a medium to large company is not something to be taken lightly. The tool and the code is not everything. The operating environment, security guarantees, SLAs, support, and a bag of features you don't need today but might tomorrow is what the SaaS offerings bring to the table.
Imagine that I run a really good software house. I can literally build anything you want, feature wise, better than most. I do it quickly. You come to me and say you want to replace Slack for your team of 200, because Slack got too expensive. I say I can do it. Because I am feeling generous and you're my good friend, I will do it for free. However, I will just give you the code, a CI/CD script, and a README.md file. I will disappear and will not maintain or support your software, nor will I give you any guarantees on how well it will work, other than a "trust me."
I wouldn't take the offer.