“...ads in newspaper site can generate some real business leads.
”
This got me thinking, and is a very good point. Someone I know well does a lively trade on eBay, making decent margins and still hasn't got bored of posting things
But advertising wise, it's a cheap and cheerful advert in the local newspaper, asking for any unwanted model train stuff. What he found is, rather than kids train sets, it's older blokes who have passed away, leaving a room full of train layouts and stuff. So he offers a price, and takes it all away.
No PPC campaigns, no SEO, no Google, just big markups by breaking up large collections into smaller lots.
So maybe sometimes we can overlook the obvious or forget more traditional avenues.