A long-awaited renovation of mortgage companies Fannie Mae and Freddie Mac could start to take shape this year, Treasury secretary Tim Geithner told Congress Tuesday. The Obama administration hopes to propose legislation to fix the nation’s housing finance system within months, Geithner told the House Financial Services Committee. The government currently finances almost all home mortgages, thanks to its 2008 takeover of Fannie and Freddie. Geithner acknowledged that devising a new system to finance US house purchases would be a “complicated, consequential” process. He emphasized that he hasn’t “seen an ideal model” to replace the current arrangement, which is widely viewed as undesirable because of its role in inflating the housing bubble and the conflict between Fannie and Freddie’s profit-seeking and public policy missions.