I have a buddy in my ward whose kid does this. I know he gets paid by those who he works for, but I also know he will mow elderly peoples lawn who need it. I don't know anything about your neighbor, but it's a great opportunity to teach your boys about service. Who knows if the neighbor is just being a jerk or if she really does have problems whether it's financial or something else. I am in no way a holier than thou guy, but I do like the idea of teaching my boy service and hard work. Sounds like your boys already have the hard work part. Just my two cents.