T.S.
First of all, you shouldn't allow your your son to accept jobs he's physically unable to do. Ten year old kids usually do things like pet feeding, plant watering and maybe a little light babysitting, not yard work!
Secondly, he WILL learn the value of hard work, you just need to allow it to happen naturally.
When my two older kids were younger (around 11 to 15) they got paid very well to pet sit, water plants and bring in mail for neighbors. When they babysat they got paid WAY more than I ever did at that age. The thing is, they KNEW they were getting paid a lot. Kids really aren't stupid, they get it. They knew that the families around here pay well because 1) they can afford it and 2) they like having a trusted and close neighbor and/or friend look after these things. I liked the fact that they were paid well for these jobs because we don't do allowance, chores are just expected, so it was nice for them to have some spending money.
Now they both have summer jobs, my 16 year old daughter is making minimum wage working 12 to 16 hours a week as a receptionist/sweeper in a hair salon, and my son (19) is making just a dollar over minimum wage as a day camp counselor 30 hours a week.
They are also putting gas in the car, so believe me, they GET it, and your son will too! Just make sure he's doing work he can do himself, that's AGE APPROPRIATE. There's no sense of pride and accomplishment in getting paid while dad does the job for him, as a matter of fact that kind of sets him up to a sense of entitlement.