Some Arizona homeowners under water on their mortgages might be able to reduce their interest rates and monthly payments if a proposed state program becomes law. The “home certificate” program laid out in a new bill is intended to help homeowners lower their mortgage payments even if they can’t refinance their mortgages through a traditional bank. The proposal is both unprecedented and controversial. Essentially, it would create a separate market for mortgage financing from private investors, bypassing banks. Investors could benefit by earning interest paid by reliable borrowers, while homeowners could benefit from lower monthly payments and lower interest rates than they currently have.