New training website or premium sub domain?

I’ ve got a pretty popular blog. I’m also deliver a training building Wordpress websites. I was wondering if i want to extend the trainings, is it better to use a new domain for all the training activities, or should i use a subdomain like 'website.com/premium/
I want to make more training stuff related to building websites, but i also want to write free articles for my blog.
I’m going to point my readers from the original site to the training. do you think the domain matters?

I think creating sub domain will be the best option as people don’t need to know another website

TO save the hassle of setting up a whole new domain and website, I’d go with the subdomain. If things really kick off you could then go to a new domain and use a 301 redirect.