How Do I Know if the Start-Up is Financially Stable?

Dear Experts, I interviewed with a start-up company yesterday. They sound exciting and have a lot of energy, but I can't get any sense if the company is stable. They are offering me a great salary and benefits, but I would hate to leave my current job where I know they are stable for this and then get laid off. How do I figure out, without insulting them, if they will be able to keep me employed long-term? Our Twitter Advice Project (T.A.P.) is no longer an active campaign. To find an answer to the above question, please use the "Search" box in the right-hand column of this website.