In his latest book Clark Smart Real Estate, Clark dedicated page after page to explaining the difficult process of figuring out if you have the best possible rate when you go for a mortgage or refinance.

The industry has made it particularly hard to comparison shop in this arena. But TransUnion's new website, TrueCredit.com, aims to level the playing field with a tool called the Mortgage Simulator.

For $10, you can buy a month of service that allows you to get a true indication of the rate you should get on a traditional 15 or 30-year fixed mortgage or refinance. TransUnion takes info such as the location of the house; the purchase price; the amount of your down-payment; your income; and your credit score into account.

Clark acknowledges that it's historically been tough to get the best deal. He's had lenders try to cheat him every which way in his real estate dealings.

Finally, mortgage rates are very favorable right now. You have real opportunity if you have a good credit score and want to refinance.