Rebelway has released the entire Week 1 lessons from their Houdini 20 Fundamentals course for free, including project files. Course Breakdown & Curriculum
You can sign up to receive free lesson samples from the actual 8-week Fundamentals course directly in your inbox.
Once you enroll in the paid version (starting around $698 ), you gain lifetime access to all lectures and a private community Discord for feedback.
The creators of Houdini offer extensive free tutorials on their official site.
– Focuses on heightfields (terrains), custom erosion, and creating stunning cinematic clouds.