Ask HN: Marketing to a Distribute​d (Niche) Market

I've gone through the process of qualifying a need for SAAS product I'm currently building that targets a niche within the (non-technical) "work from home" market. And while I've gotten great feedback/support from 50 or so folks looking to sign up when we launch, its the other thousands/millions that I want to reach, but am struggling to do so.

The "work from home" market is fragmented, with a few forum sites here and there that I've been able to target, but most won't permit you to post sales/marketing info, and I don't want get our product misconstrued as spam.

I just see that with so few places to go to target a larger audience all in one spot, its going to be difficult and resource intensive to go from 50 to 5000.

Any thoughts/advice is greatly appreciated.