Ask HN: Need some start-up career advice.

I'm currently running a solo start-up right now after about 4 iterations through 3 years (the product line changed, and my partners went their separate ways). The newest product line being launched is a menu service where restaurants can easily host their menus online, and use a raspberry pi to create a digital menu billboard in the restaurant so when they update their menu, their signage in the store is updated instead of having permanent price menu facades. The goal is to charge a subscription fee. The menu service has free nutrition formulation in it, so restaurants can help develop healthy healthy menus and eventually choose to display calories if they want. To make ends meet, I have been doing some part time rails consulting on the side of about 10 hours a week. Recently, I got the opportunity to do a 3 month full time rails opportunity. After running the start-up for so long, and not having a successful product so far, I sometimes have doubts on whether it will succeed or not, and if I should hedge my bets to make some more money on the side. I have been struggling whether I should just go ahead and do the 3 month gig, or still stick with the 10 hour a week deal and really really try to get the new start-up idea off the ground. The only thing which is so painful, is after working on a prototype concept for about 2 months, I go out to the businesses, and see that what I made isn't something they wanted. I know I am rambling, but any two cents on this situation would be appreciated.