commissions don't just roll in... if you quit meeting customers and doing your thing, then you'll lose the "passive" income very quickly
We have a small mfging facility, so I'm on the other side of it. A wholesale account can spend years building up their business, but If they take a day off to go on vacation, their "loyal" customers go to another wholesaler. That's if you take one day off (or even hours) because customers are impatient. this also happens with salespeople on commission.
I repeat, there is nothing like passive income without work... there is always someone willing to do the same thing for a few bucks less. If you can do it for $1000/month, but don't need to put in any labor, there will be a company willing to do it for $500/month... it's the benefit of a capitalistic society.
Now, if you can get a monopoly on something (they can only buy through you) and their is no suitable alternative item available, that's where you could make money fairly passively..