Week Based Subscriptions

I just signed up for ghost to create my premium email newsletter. I was deciding between Memberful and Ghost.

On Ghosts page where it describes its members features (https://ghost.org/members/) it says you can collect recurring subscription revenue on a weekly basis as well as a monthly/yearly one.

However when trying to setup I did not see this option? is there a way to do this, or am I just missing it?

Another key feature that I was looking for was being able to offer trial subscriptions, as you can in memberful. (try 1 week free, etc) Not sure if that is possible yet?

Are these features available on ghost? If not I unfortunately may have to switch to memberful for the time being as these are crucial features for me.

Thanks for the help