Debt collector Credit Corp has maintained its strong earnings momentum, reporting an 18 per cent increase in net profit for the six months to December, after increasing its profit by 21 per cent in the year to June.The company's core business is purchasing distressed debt ledgers and putting its collections team to work on them. The company spent a record A$86.5 million on debt ledgers in the December half and this helped drive revenue growth, which was up 25 per cent.Credit Corp made a net profit of $17.2 million, on revenue of $84.1 million.Another source of revenue growth was the company's consumer lending business, MoneyStart, which was launched in 2011/12. MoneyStart provides secured and unsecured personal loans to borrowers with impaired credit histories. The loan book has grown quickly, from $19 million at the end of June to $35 million at the end of December.Credit Corp's chief executive, Thomas Beregi, said the lending business would make a profit in 2015, "as monthly lending revenues now exceed the upfront life-of-loan loss provisioning on new loans."It was not all good news for the company, however. It has had to consolidate its fledgling US debt collection business, which was opened in 2010/11, closing one of its offices in the face of "challenging" conditions.And Credit Corp was highlighted in the Credit Ombudsman Service's annual report as one of the member organisations attracting a high level of complaints.With the release of its financial report yesterday, the company upgraded its earnings guidance. In November it said it expected net profit for the 2013/14 financial year to be between $31 million and $33 million. Its expectation now is that it will earn between $33 million and $35 million.