I guess the question is who is your customer or more specifically who's your buyer, who's your user and where do they hang out ? Also how do people find out about you product ? Distribution takes time, so I think its important to gauge interest upfront rather than commit to building first.

In general, the answer usually is to find people in your own network. If you go by that funnel the first thing you need is a network. LI is great at this. The next thing is to see who in your network is worth talking to. Find out whether the pain-point that you recognized resonates with them. A LI blast to your network might work as well to give you a bit of credibility. One thing that is cited often that does NOT work is spamming people asking for their time to learn about a problem. Nobody ever got back to me wit this method. But asking people in your own network for warm intros almost always works.