A quart is 2 pints. A pint is sixteen fluid ounces of water and weighs about 16 ounces (avoirdupois weight.) A gallon is 4 quarts (8 pints) and thus weighs about 8 pounds. Five gallons would be about 40 pounds.
In some cases, if your mother is on Medicaid, she can designate you as her personal home care aide and you can get paid a small amount through Medicaid. If your mother has her own resources, you can draw up a contract agreeing to work as her home health aide and she can pay you a salary that you both agree upon.
Medicaid will look at any transfer of assets she's made in the previous years. If assets have been given away, or transferred for less than full value, during a look-back period before applying for Medicaid, your mother may be ineligible for Medicaid nursing home coverage for some period of time.