There are variety of issues that need consideration here before you make a decision.
A. Where are you in life-- just getting started, new babies, mature, junior high kids or empty nesters with kids in college?
B. How much money is involved? More than you make now, less than you make now? About the same?
C. How secure is the start up? Are they fully capitalized, undercapitalized or just enough to make it?
D. What is the competitve market in which you are entering? Do you know the industry/market? What is the local, regional, national, international competition like?
E. If you take the job, the start up fails, can you find another job. Look at A above-- if you are 60 years old and am a empty nester, the job world is kind of cruel-- fact, not opinion.
F. If you take the job and the start up fails, can you take what you learned and parlay that into something better than you had before you started and better than the startup?
G. With any start up, the hours are long, the resources are constrained and there is always more requirements for resources than available resources. Can you handle that?
If you can answer these questions, honestly, you will have a better idea on how to proceed.
Good Luck!~