Wiktionary
n. The act of selling something previously purchased.
Usage examples of "selling on".
In six months, I'll have the patent and I'll stop selling on the street.
The three hundred thousand bucks was left to me before I was born by a grandfather who made a fortune selling on an international scale.
No more will international police and your hired security organizations fight sham battles with people you label criminals because they engage in your artificially created myth of smuggling and selling on what your little playmates have concocted as the great and terrible illicit diamond market.
Although I couldn't wait to leave school once and for all so I could join Granpa permanently, if I ever played truant for as much as an hour he wouldn't take me to watch West Ham, our local soccer team, on Saturday afternoon or, worse, he'd stop me selling on the barrow in the morning.