Are you willing to help him alter his lifestyle to make better use of the money he has (very low probability of success) or teach him how increase his income (also very low probability of success)?

If a tenant chooses not to use the vent, that's on them.So, provide a quieter fan if you just don't want to deal with it (which would be my choice) or give a written warning to the tenants that disabling the fan is a violation of their lease agreement (I'm sure you have a clause about damaging the property or making alterations without permission), and they need to knock it off - and that any damage resulting from them disabling or not using the fan is their responsibility.And of course, you can always not renew their lease.

@Daniel Lehman, now that there's more information on the table, I think some people might alter their advice a bit.

My lease states (removed the parts not at all applicable):Deductions:(a) damages to the Property, excluding normal wear and tear, and all reasonable costs associated to repair the Property;(b) costs for which Tenant is responsible to clean, deodorize, exterminate, and maintain the Property;(f) unpaid pet charges;(q) cost to restore walls, flooring, landscaping or any alteration to the Property not approved in writing by Landlord; and(r) damages to the Property caused by smoking, including but not limited to stains, burns, odors, and removal of debris.Here's a photo of one of the door frames, for example.

You may even be able to demand they be altered (neutered or spayed).

Usually due to a life altering issue.

Also the lockbox so the downstairs tenant cannot alter the temp for the upper unit.

Could you recommend a good comprehensive lease agreement specific to Texas that I can also alter and make changes?

It's not that these are dumb request, it just irritates me when tenants expect you to do expensive alterations without increasing the rent.

@Remington Lyman Just fyi, cameras dont do much unless its motion as activated with alters.