In a strategy to make credit more available to home buyers, the Treasury dept will purchase mortgage-backed securities from Fannie and Freddie since they are the major source for lending institutions. However, credit scores will play a major role in who gets approved or not. A person's credit rating can range from 300 to 850, with 300 being very low and 850 being the best. Only those people with the highest credit scores are getting the best mortgage rates and terms.