I don't think there is anything wrong with starting a business in your 40s, or at any age, but it certainly is important to know the risks. I've been a business coach for over 20 years. I specialize in new startups. My youngest client was 14. My oldest 71. But one thing I've said to people on the fence, the younger you are, the less you earn in a full time job now, the lower the bar to "success".