Do you post? I live rural so suspect buyers maybe limited, although I have got rid off all my very old, low value bikes easy peasy...dirt cheap though!. I have a Thorn I am flogging on
ebay via the £1 deal, collection only. Lots of interest. 2 buyers bike to small one every thing right but didn't read the "collection only no PayPal". I intend on leaving it on as it will sell in spring. Relist everytime they offer £1 maximum deal (normally every 2 weeks. Either way your sons business sounds like a nice little earner. A good way to start.
You/he might try this. Ebay via baycrazy or mse equivalent. These sights look for collection allowed. In there there will be collections only. They go very very cheap. As a lot can easily be resold at a decent profit if you are willing to post. If I set within 10 miles around me I will only get 200 at most. In a city I would get 2000 plus 5 miles from me. I occasionally did this when I stayed in Manchester. One item 99p sold at £108. I never bid myself I use a bid sniper like Gixen, that way you don't get into bidding wars. Try the site but dont put anything in the search as you don't have to.