When I did a marketing degree in the late 1990s, I remember being taught about researching the market through things like focus groups and surveys of the target market.
This approach is still valid, and gets fast results, however in the internet age there is a cheaper alternative way to find out if your product or service is something that people want.
Set up a carefully written webpage that targets the keywords and phrases that your potential customers might be looking for.
To be continued, when I have more time 🙂