Does having a car loan affect the amount of money we would be able to get for a mortgage? And is it better to focus on paying off the vehicle loan, or saving money for a bigger down payment on a new house? –K.F.

Yes, your car loan could affect your prospects. A mortgage lender will assess whether you'll reasonably be able to carry the home loan you're going for based on your income and other obligations—of which the auto loan is one.

Classic underwriting guidelines hold that housing debt should make up no more than 28% of your monthly household gross income, and that total debt should be limited to 36% of it. "There are compensating factors, however, which could include a bigger down payment, your credit score, and cash reserves after you've purchased the home," says Mark Goldman, a mortgage broker in San Diego and lecturer at San Diego State University. "So it's not uncommon to go a bit higher, even into the low 40s."

What these calculations show the lender: "If they give you this mortgage, will you have enough income to make all your monthly payments?" says Tom Quinn, Credit.com's credit score expert. If the addition of the mortgage would really stretch you financially, the lender may deny your application.

As to your second question, you're better off saving for a larger down payment. For one thing, if you aren't able to pay at least 20% of a home's purchase price, you'll have to pony up for Private Mortgage Insurance, or PMI. But also, the bigger your down payment, the less you'll have to borrow. "In the long run, over a 30-year fixed mortgage, that's going to save potentially thousands of dollars in interest payments," says Mary Lacey Gibson, a financial planner in San Juan Bautista, Calif.

--Kate Ashford

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