Since about age 9 for pocket money and chores, but DS is a really easy going lad, and because I have always carried through with promises and threats, he knows I mean what I say, which really does help.
It's not to late for you guys though, being consistent and following through is the key, as he will respect what you say as he knows you mean it.
You will have teething problems, ask him what he wants out of the situation, explain what you want and come to an agreement.
Be consistent and follow through again and again and again.
My 7yr DD knows the score as well, she knows I will follow through. She was a nightmare toddler and this was the only way I could handle her. She was very manipulative, if I waivered she took advantage, if I gave an inch she took a mile. She is the sort of child that if you offered a biscuit she would ask for two, if you offered three she would want four, if you said you would read one story she would want two, nothing was ever enough, so I put be foot down and remained firm and strong.
I do praise them both a lot and reward them, so it works both ways, if they have done extra voluntary jobs they get a bit extra pocket money. If they get good reports from school, or special praise from school, I praise them, tell them how proud I am and make sure they hear me telling nanny etc.
Works really well for us, they are both very very well behaved children who I would take any where and know they will make me proud.