20 minutes isn't enough time to get competent and spend hard earned money on any membership. That's a slow slog.

Maybe the best thing for you to do is get Rocksmith 2014 (currently on sale with cable for $40 on Amazon). That'll teach you rhythm and an overall feel for the path that you may embark upon. It's a lot of fun and you will learn rock songs through it.

I use it every day along with actual lessons.

Check it out:

https://www.youtube.com/watch?v=2NWZR3rh06c&list=PLkTijIFpb637_jSnwBpwghkRIQrNanu3t