My mother cares for my dad who has Alzheimer's disease. She wants to keep him in his own place for as long as possible. She gets a little overwhelmed and finds her patience short, at times. She has to take him with her everywhere with her, for fear he will wander off. I would pay to have someone come by and help with errands and light housework to take off some of the load.
Please note that caregiving Agencies are expensive, but they are also licensed, bonded, insured, and most carry workman's comp for their employees. The one that I use charges $28/hour.... some Agencies will charge for mileage when it comes to running errands.
It sounds like your Mom might need to start looking for continuing care facility for your Dad, as eventually Mom would need someone there all day, and maybe into the night if your Dad won't sleep at night. Otherwise, your Mom would get only 2 or 3 hours of sleep at night. If your parents can afford around the clock care, which could cost up to $20k per month, then choose that. The night caregiver job is to stay awake all night and to help your Dad should he wander around the house.