These are my checkpoints, in order of priority
Is there core team stability? Does the founding team still have the ability to inspire (even a small group of people) to believe in their dream? Do the founders continue to exhibit the values that made me engage with them in the first place?
Is there genuine customer traction? Is it growing because the team is applying their learnings to the product / service?
This is a tricky one. I have seen some fantastic people and ideas falter because they lack the ability to raise capital. It’s good to understand early where funds will come from. It doesn’t always have to be big-ticket VC cheques.
Personally, if I sense the first one happening, I would cut-off ties immediately. I would try and work through the other two to see if there are possible solutions.