I'm working on just such a product for professional electronics engineers, though it's a $500M/year niche, so could scale way beyond $5K/month .

Personally my advice would be to quit your job and go and work in an existing industry you think you might be able to disrupt with software, it's the only way you'll learn the real problems.

I did this the other way around by working as a hardware engineer for 10 years then getting into web dev. I spent some time thinking I'd wasted the start of my career but now realise it's the best thing I ever did.

If anybody is looking for a problem to solve I've got one so get in touch. This isn't the next Twitter for Groupon, I'm working through some hard problems so please dont waste our time ;-)