First, I think you have to understand your own motivations - are you interested in pursuing this as a serious side project and/or startup? You found something

First, I think you have to understand your own motivations - are you interested in pursuing this as a serious side project and/or startup? You found something interesting, a real or perceived market imbalance. If there really is a shortage of talent, and a shortage of jobs for people over 30, you could provide a curated pipeline. Now you have to find the other side - a job board is a two-sided marketplace, and those are hard. I'd talk with recruiters and HR people. Also with people that have been involved with job boards. I'd try to find a mentor among those. As a 35-year-old myself, something that you would have to address is prejudices on both sides of the equation: companies that believe that "old" programmers are no good, and developers that believe that company X is a "bullshit" job (most older developers will be pickier).