The following chart shows the spread between 30 year mortgage bonds and 30 year treasury bonds. The spread means the difference between the two.
Imagine you have $400,000 to invest today. You have two options. They both will make interest payments to you every month for 30 years.
1. Lend an American home buyer $400,000 that they can use to buy a house.
2. Lend the government $400,000
At today's rates you will recieve only .5% more in interest by lending to a home owner vs. lending to the Federal Government.
Can you see how artificially low mortgage rates have been suppressed by the Federal Reserve buying?
No intelligent person would lend to a risky home owner vs. lending to the government for a difference of .5%.