Do we have to pay for month to stay in the gym

Yes

You can also get a visitor's pass

Yes, I believe so.

I believe you can pay for a single visit. It's not cheap, I believe it's like $10 or more

Yes, you do have to pay, it is a business, it's not free.

Yes, there is a membership fee

Of

There is a membership fee. If you commit to a year it's cheaper per month