My question is, what is the best way to evaluate a software startup as a perspective employee from the point of view of viability i.e. economic viability.
I am more interested in hints related to trait characteristics that are big indicators of how viable the startup is.
I imagine noone is going to show the deposits in the bank...
When interviewing just ask them point blank: how does the company make (or plan to) make money? If the company is not yet profitable: how capitalized is the company? If they can't answer or have poor or vague answers then it's probably not a place you want to work.
A fellow software developer friend of mine interviewed at a startup (if you want to call it that) a couple years ago. The company was offering a high salary, but had a dubious business model, and he was do be employee #1. Needless to say, he had legitimate questions and concerns about the viability of the business since he didn't want to be out of a job in 3 months. When he started asking questions about the company's finances and revenue model, the CEO started getting touchy/feely and offended. Ultimately, he never heard back from them. Probably the best thing that happened to him cause the company is out of business.