Background information: I'm looking to start an entrepreneurship. My goal is to generate a net revenue of $4000/month (for example), probably through a SaaS software offering (think GMail).
My question is: how do I tell if my market is viably large enough? I've done market research, looked at competition, pinned down an idea, and talked to a couple of people about it. It seems like (maybe) the need is there. But how do I engage in customer validation (does it solve their problem), and even then, verify that there are enough people or enough of a market out there to make this project worthwhile?