More Than the Mortgage: Don't Forget Other Home Costs

Homeowner's insurance is another typical addition to the monthly mortgage payment. In 2005, the national average for insurance premiums was $764 a year, according to the Insurance Information Institute. But this figure varies considerably among states and even among zip codes.

As a rule, you can expect to pay about $300 per $100,000 in home value. In this instance, that would mean an extra $750 a year, or $62.50 per month.

That bumps your monthly mortgage payment up to $1,512.89 -- more than $300 above the original figure.

Maintenance and Repair

As a renter, you don't need to worry if your furnace breaks down or a tree falls across your front lawn -- you can just call your landlord. But as a homeowner, maintenance and repairs can have a big financial impact if they haven't already been factored into your household budget.

Some major repairs happen on a relatively predictable timeline, making it easy to save up money in advance. A roof, for example, will last 12 to 20 years, and a furnace typically lasts about 20 years.

Other maintenance costs are less predictable. In order to avoid busting your budget if your basement floods, set aside funds to cover general household maintenance, which can total 1.5% to 4% of your home's sale price every year.

If your $250,000 home is relatively new, you could assume your annual maintenance will be about 2%. That means you should save $5,000 a year -- or an extra $416.67 a month -- for upkeep.