Can a 17 year old join this gym

Yes

As long as you have a bank account and/or debit, or come with someone with a black account.

Can i come with my older brother

When my son was 17, I used to regularly bring him to work-out as a guest with me.

I have seen people bringing them in as a guest.

Guardian required

No a 17yrs cannot join the gym but you can bring them as a guest a parent must accompany them and show proof of childs age with birth certificate , permit or lisence

I think it is a 18 and older crowd.

Unsure