Getting paid
Every ad payment includes a flat service fee, shown wherever a payout is displayed — on the review page before you accept an ad, on the pay page an advertiser sees, and in your notification emails. It's not a fee on top of what the advertiser pays; it's taken from the payment itself, and Stripe splits it automatically so the rest lands straight in your account.
There's no fee for creating a space, no monthly charge, and nothing owed if an ad never sells.