Although mortgage production volumes appeared to remain fairly stable during the first quarter of this year, corporate revenues and earnings from the home loan business veered sharply higher, according to a new Inside Mortgage Profitability analysis. Based on a review of first-quarter earnings statements from 15 major lenders, mortgage revenue appeared to jump 38.5 percent from the final three-month period of 2002. The 15 companies in the sample reported a combined $3.67 billion in