There is another side to your market -- the job board whose customers are not the unemployed but rather the companies who want to hire them. You could charge companies or recruitment agencies for "premium listings" while allowing them to post basic want ads for free.

The other way to profit, I suppose, is to use the knowledge and data gained from the app and leverage it into some kind of personal income. For example, maybe you run an employment agency of your own, and draw on the site's database for leads. The app continues to be free, and you are just cherry picking the best from it.