Build and iterate the idea, and your understanding of the type of person that would want to buy it. Make each iterative step as you gain enough confidence to invest the time and money needed to take that step.
For instance, you can start by asking friends and family while it's still just an idea. If it seems to have promise, maybe make a landing page for it for free on somewhere like Weebly.com.
Start showing the landing page to friends and family again, but also to strangers now, and ask their opinion. Iterate the landing page, and prices etc. based on this feedback.
Maybe then build an online survey that you can circulate to more anonymous people within your theorized target demographic. See how they respond, and iterate the idea, website, and target demographic if needed.
Then see if you can get people to actually sign up. Contact everyone you've talked to up until now and show them the now polished website, idea, etc. and offer it to them at an early bird discount. See if anyone bites.
Let me know if you'd like more specific help with any of those steps, with regard to your specific idea,
If you're not 100% sold on the idea, figure out what the ideal marketing offer would look like to promote this service. Then, launch a niche Facebook ad campaign at your ideal buyer and see what kind of traction you get.
This will help you determine if the interest is there before you go all in. It'll also give you a small list to sell to once the service is real.
1) Setup a WordPress site with Paid Memberships Pro
2) Add WP Courseware, if you're adding videos to each subscription/membership level
3) Drive traffic to site. Might be via talks to Meetup Groups or Facebook Ads or Traffic Oxygen campaigns.
If you provide more specifics of what you've already done + your target outcome, likely many more people can provide assistance.
Utilize Cratejoy to test your concept. Once you are confident you've proven your concept, transistor over to Shopify and the Recharge app to grow your business. Shopify offers a host of apps to help run and grow your business that Cratejoy doesn't.