Alarming Keywords: elderly [easily taken to the cleaners], mother in law [female], handyman [is this person an electrician?], no electrical problems [if it works, don't fix it].
Get a picture of the electrical box including neutral bar and post it on the internet if possible. Or electric company may examine it for free. Or have a qualified electrician check out electrical box.
What other work is this person doing for your mother in law and what is he charging her?