Technology is a very volatile industry, with many products failing to launch or going bust, while others are sold for millions or even billions. With so much risk involved, investing your time and money in a project can be a gamble, but one that can be hugely rewarding!
You can offset some of the risk involved by negotiating a deal with your developers. These days, some developers are willing to substantially reduce their rates in exchange for a share in your project. If your app is a hit, everyone wins! If it's a flop, you don't lose as much as you could have.
Think about how much of this idea, if any, you'd be willing to share with others in return for a much cheaper development rate.