Living your purpose does not have to be in opposition to supporting yourself. Ideally you will be able to earn your living by living your purpose. But, to address the question, let us assume that your purpose is not going to generate any money for you. The answer, then, is to find a way to make a living that will still allow you to pursue your purpose. Include as much time pursuing your purpose in life as you are able. By still continuing to pursue your purpose you will be creating more meaning in the "job" that enables you to continue to pursue your purpose.

Also, keep in mind that there will be many ways that you can live your purpose. You will most definitely be able to find some way to bring a sense of purpose to your "job", whatever that job is. Doing a job purposefully will bring much greater satisfaction (and rewards) than doing the same job mechanically.

"The biggest mistake people make in life is not trying to make a living at doing what they enjoy most."
Malcolm Forbes

"Find your passion and connect with it, whether or not it brings you money. Ultimately it will lead to the full experience of what you were born to give."
Donna LeBlanc

"Success is not the key to happiness. Happiness is the key to success. If you love what you are doing, you will be successful."
Herman Cain