Tina Tower explains how to test a course idea without spending money: talk directly to people who might take it. Skip surveys and formal research. Start small, listen to what they actually need, and adjust from there.
Thinking about a new course. Please don't build it in a vacuum. The simplest way to validate your idea before you build anything is to talk to your people. Open up your DMs and emails and ask people, if I created something that helps you with whatever your idea is, would that be valuable to you? You don't need a survey. You don't need all the fancy pants research. You just need real conversations, one on one with the people that you want to serve. And if no one says yes, you've saved yourself weeks of work. And if they do, you've got proof that want to buy it before you start building it. So start small, start scrappy, but always start by listening.