Commonwealth Bank has locked John Symond into his role as executive chairman of Aussie Home Loans for four more years, as part of the deal, announced yesterday, which sees CBA take control of the mortgage broker and originator.Commonwealth Bank will increase its stake in Aussie from 33 per cent, which it acquired in September 2008, to 80 per cent, with the right to move "subsequently" to 100 per cent ownership. An Aussie spokesperson, Fiona Hamann, said Symond would continue as executive chairman "for at least" four more years.Commonwealth did not disclose the purchase price of its latest 47 per cent stake. After buying its initial one-third shareholding, in 2008, the bank put a value of A$71 million on the investment in its 2009 annual report, suggesting the entire business was then worth more than $210 million.At that time, Aussie managed a mortgage portfolio worth $24 billion. In a release issued yesterday, Aussie said it had 250,000 customers and a portfolio worth $53 billion. But while Aussie has doubled in size over the past five years, commission rates on loans have fallen - making mortgage-broking a less profitable business nowadays.According to Fairfax broadsheet newspapers, Aussie's 2011/12 profit was $32.6 million, down from $51.7 million in 2010/11.These numbers suggest a value of between $300 million and $450 million for Aussie Home Loans, and more than $150 million for the controlling stake bought yesterday by CBA. The Australian Financial Review suggested CBA had paid $200 million, valuing the total business at around $420 million. Fairfax's broadsheets said CBA was believed to have paid "in excess of $160 million" for yesterday's stake.With CBA's financial backing, Aussie acquired a $2.25 billion loan portfolio from Wizard in 2009, and this year it bought an aggregator, National Mortgage Brokers, with a portfolio worth around $8 billion.In a recent report on the mortgage sector, Deloitte forecast more consolidation among mortgage brokers as they attempt to grow their share of the market for new loans.Aussie played an important role in reshaping the Australian mortgage market in the years after its 1992 founding, pressuring larger banks to drop their rates in the mid-1990s.