Focusing strictly on your question about untaxed income, as others have said, what you are doing is considered self employment and is taxable income and is supposed to be self reported on an income tax return as such. I do not expect you to know that, and I don’t necessarily expect your mother to know that. The majority of the population uses a tax preparer and knows nothing about tax law. If your mother mentions it to her tax preparer if the tax preparer is ethical he will explain that it is taxable income. If your mother uses online software and reads all of the questions and answers them honestly the software will also include the cleaning as income.
That aside, there must be some other sources of income in addition to your mother’s 20k job and 1k in cleaning for you not to even be receiving free lunch?