You need to stop asking the same questions over and over. We've already established that an occupancy fee is legal because it is not prohibited under the Austin Fair Housing ordinance and it is not discriminating against a protected class, regardless of how much you wish it so.
The real issue is whether it's a one time fee or a monthly fee which is strictly a contractual issue and, as I wrote earlier, you are welcome to post a copy of the lease for a comment on that issue.
Or you can file a complaint with Austin Fair Housing Department.
Or, you can just not pay it and see how that goes.