Here's the thing most people aren't looking at: your mortgage rate is only part of your interest picture. If you're also carrying $40,000 or $50,000 in credit card debt at 22 or 24 percent, your overall cost of borrowing is much higher than that 3% suggests. The mortgage rate looks great in isolation. It looks a lot less impressive when you add up everything else you're paying.

Here's a frustrating situation I see all the time. A business owner comes in to apply for a mortgage. Their business is doing well. They're pulling in solid revenue, their accounts look healthy, and by any common-sense measure they can clearly afford the payment. Then the underwriter pulls the tax returns, sees the write-offs, and the number on paper looks nowhere close to what they actually take home.

I talk to first-time buyers every week who come in convinced there's a specific loan product called the "First-Time Homebuyer Loan." They've seen it on social media, heard about it from a friend, maybe even read about it on a lender's website. And every time, I have to deliver the same news: that loan doesn't exist.