He still owns around 1,500 Harry Potter books - including a first edition bought for just a PENNY and signed by J K Rowling herself.
His collection consisting of other original editions could fetch up to £5,000 when they go under the hammer at Hansons Auctioneers on December 12.
The book signed by J K Rowling, is expected to fetch between £1,800-£2,500 while ten hardback first editions of Harry Potter and the Chamber of Secrets could make £800.
Mark has been making a living trading Harry Potter novels for the last decade following a chance discovery courtesy of his daughter Holly, now 25.
The dad-of-five, who is married to Julie, 51, said: “When Holly was a child, she loved Harry Potter books and started her own collection.
"About 10 years ago, we decided to sell some of her older books and three of them were snapped up within 20 minutes on eBay for £9.99 each.
“I’m a businessman with a shop in Buxton and I knew this was a business opportunity.
"I checked the ISBN numbers and sourced the same three books second-hand on Amazon, bought them for a penny each plus postage and sold them in minutes for £9.99 each on eBay.
“It turned into a business. I started buying Harry Potter books for next to nothing at charity shops and online.
"I turned them into sets relating to the different editions and sold them on eBay.
“I realised through dealing in Harry Potter books that people like to have a book from every print run to complete their collections and the same goes for all types of collections.”