It is perfectly legal to ask your employer, and perfectly legal for them to pay you less--they can agree to do this at will. (It would be wise for them to get your request in writing, since that will protect them if you then turn around and try to claim disability-based discrimination.) There is no law saying that all employees must be paid the same. They could refuse to do this, but you can ask, and they could choose to comply. Obviously, you must be paid at least minimum wage.