My question involves landlord-tenant law in the State of: Texas

My parents just moved into a 55 and older apartment. Their lease has a monthly rent payment specified and in a section called "Other" on the lease, it specifies $150 dollar occupancy fee. It does not say this is a monthly fee it just specifies a $150 Occupancy fee. In the "Other" section it says, key replacement $15.00, garage door opener replacement $50 dollars. All fees specified in the "Other" section are one time fees. The leasing office is claiming that the occupancy fee is a monthly fee although it does not say that anywhere in the boilerplate lease. If they were to charge more for two people wouldn't that be reflected a higher rent payment? How does one interpret a $150.00 occupancy fee? Monthly or one time?