If you can't find your target market, you might want to consider a different demographic that you understand better. Most successful startup founders started a business specifically to solve the problems they dealt with at their last job. They understand their product market fit because they ARE their target market.
First step is guessing who your customers might be.
But sure, I'm working on things for parents/students, home buyers, and DIY heat pump installers.
* Parents/students hang out at schools and are probably a good referral/recommendation crowd
* Home buyers are looking for mortgage comparisons on Google (but that's probably a terrible strategy, since this is a highly lucrative segment to market to, so you should expect high customer acquisition costs)
* DIY heat pump installers will probably look at ads on /r/DIYHeatPumps