Depends on the product, depends on the potential market size, depends on the founders, etc. And you can definitely have traction and an initial revenue stream

Depends on the product, depends on the potential market size, depends on the founders, etc. And you can definitely have traction and an initial revenue stream without having product-market fit in a meaningful way. You can survive for years on a large-enough group of savvy early adopters (and get funding based on that initial enthusiasm), but if you don't cross the chasm, your revenue stays flat.