Investment in new business lines and a conservative approach to provisioning retarded profit growth for specialist financier Thorn Group in the year to September 2012.Thorn reported growth in revenue of two per cent over the year. Net profit fell two per cent, to A$14.0 million. Earnings before interest and tax increased three per cent, to $26.3 million, mainly because of good trading in Thorn's established Radio Rentals operation.Cash earnings fell for NCML, a debt collection company Thorn bought in 2011. Earnings increased for Thorn Equipment Finance.John Hughes, chief executive of Thorn, said that it was "building revenue streams from CashFirst, and Thorn Equipment Finance is really building a book. There's investment in people and systems before you reach a critical mass."The Thorn boss revealed the equipment finance arm had receivables of $236 million - a figure which is "yet to convert to earnings", according to an investor presentation. Hughes said an initial target for receivables was $50 million.But, he said, Thorn was "providing for bad debts at four per cent", which was "probably double what it will be"."All that comes at a cost to profit," he added."Major finance houses are so risk averse; they want to minimise their risk-lending on motor vehicles or houses. It leaves the way open to others to present people with a big opportunity," he said.Hughes said Thorn would open five more Radio Rentals outlets this year. The company is renegotiating its funding, provided by Westpac, with a view to extending the term, Hughes added.The result took the market by surprise and Thorn shares dropped more than 11 per cent, from $1.94 to $1.72, in the space of half an hour. They recovered a little later on to close at $1.78 yesterday.