Have mortgage rates bottomed out? It may be time for home buyers and their agents to pay close attention and lock in a rate.

Compared with last week’s historic lows of 4.78 percent for a 30-year fixed-rate mortgage, rates were slightly higher this week, Freddie Mac reported today. A 30-year, fixed-rate averaged 4.84 percent with 0.7 point this week, according to Freddie’s weekly survey of lenders across the country. However, that rate is considerably more attractive than the 6.05 percent a year ago.

A15-year fixed rate mortgage offered this week’s most affordable rate – 4.51 percent with 0.7 point – a small rise from last week’s 4.48 percent, but better than the 5.6 percent over the same period a year ago.

"Mortgage rates rose slightly this week amid positive economic news that the economy may be approaching the bottom of the recession," said Frank Nothaft, vice president and chief economist at Freddie Mac.

To qualify for these rates, home buyers must post a 20 percent down payment. Those who can’t afford to put that much down will face higher rates, as will borrowers of loans too big or risky for Freddie or Fannie Mae to purchase.

Under adjustable rate mortgages, a five-year rate was 4.9 percent, 0.6 point, up from 4.8 last week and a one-year ARM was 4.78 percent with 0.6 point up from 4.77. A year ago, the five-year ARM was 5.67 percent and the one-year was 5.29 percent.