Depending on where you are, it still may not be legal. Law overrides contracts.

If you’re in the US, unpaid overtime is only permissible if you’re salaried exempt. To be salaried exempt:

• you must make at least $684 every week ($35,568/year)
• your primary job responsibility must be one of the following:
  • executive - managing the enterprise, or managing a customarily recognized department or subdivision; you must also regularly direct your work of at least two FTEs and be able to hire / fire people (or be able to provide recommendations that are strongly considered)
  • administrative - office or non-manual work directly related to the management or general business operations, or
  • learned professional - work which is predominantly intellectual in character and which includes work requiring the consistent exercise of discretion and judgment, in the field of science or learning
  • creative professional - work requiring invention, imagination, originality or talent in a recognized field of artistic or creative endeavor
  • IT related - computer systems analyst, computer programmer, software engineer or other similarly skilled worker in the computer field
  • sales
  • HCE (you must be making at least $107k per year)
• your pay must not be reduced if your work quality is reduced or if you work fewer hours
  • for example, if you work 5 days a week, for an hour a day, you must get the same pay as if you worked 8 hours every day. There are some permissible deductions they can make - like if you miss a full day - and they can require you to use vacation time or sick time, if you have it - and of course they can fire you if you’re leaving without completing your tasks… but they still have to pay you.

Check out https://www.dol.gov/agencies/whd/fact-sheets/17a-overtime for more details on the above.

It’s quite possible you’re eligible for back-paid overtime.

Note also that the minimum exempt wages are increasing in July.

Re your “cover my expenses just to exist” bit and the follow-up about employers catching on and pushing abusive shit… if this is related to a disability make sure to look into getting that on record and seeking an accommodation. If your primary job duty is X and they’re pushing you to do Y, but your disability makes Y infeasible, then it’s a pretty reasonable accommodation to ask to not have to do Y (assuming your HCP agrees, of course).

Just because it is in your contract doesn't make it legal!

Realistically it could be worth checking your local laws regarding it and potentially speaking to a lawyer as some will do a free consult to see if you have a case