The declining home values that are plaguing homeowners are just one of the factors creating an opportunity for prospective home buyers.

Standard & Poor's latest Case-Shiller index, which tracks home prices across 20 major U.S. cities, reported that values dropped 19% in January from a year earlier.

Those depressed values, combined with near-record-low mortgage rates and government incentives (an $8,000 first-time home buyers' tax credit included in the stimulus bill), are luring more first-time home buyers into the market. Indeed, a recent Century 21 Real Estate survey found that more than three-quarters (78%) of potential first-time home buyers say now is a good time to buy.

If you agree, be aware that buying a home comes with plenty of potential missteps. Here are 10 all-too-common mistakes first-timers make.

1. Not knowing how much house you can afford.
Many novice home buyers spend a lot of time researching homes — comparing kitchen layouts and backyard square footage — but very little time researching their financing options. One of the first things buyers should do is talk to a qualified lender and get pre-approved for a mortgage, says Claire Clark, senior vice president of business development at Prudential California Realty. Without first figuring out how much house you can afford, you risk falling in love with one you can't.

2. Assuming foreclosures are great deals.
Just because the previous owner owed $450,000 on a house before the bank took it over doesn’t mean it’s worth that much now. Values have slipped significantly, says Jay Michael, partner at Estate Property Group, a Chicago real-estate brokerage, so you may not be getting the bargain you think with a foreclosure. Also, most homes owned by lenders or banks have been sitting vacant for months and may have been vandalized. That could require extensive renovation or repair. Weigh the costs of fixing up the property against the savings you’ll likely reap by buying a lower-priced foreclosed home.

3. Letting your true feelings show.
No matter how much you've fallen in love with a house, don’t let the seller’s agent in on it. Otherwise, he will gain the upper hand in negotiations.

4. Failing to find a good buyer's agent.
Landing a mortgage is tough these days. So buyers should rely heavily on knowledgeable agents to help them get their finances in order, says Michael. After all, buyer’s agents have a fiduciary responsibility to the buyer exclusively — and should be looking out for his best interests.

5. Underestimating the costs of owning a home.
Whether it’s a rusty pipe or a leaky roof, things go wrong and need to be fixed. Many home buyers don't anticipate the additional costs for repair and maintenance, or for an increase in utility costs, says Erin Baehr, a certified financial planner and president of Baehr Family Financial. Consider the age of your new home and how well it’s been treated by the previous owners in your budget. Be prepared to set aside a small percentage (1% at most) of the home’s purchase price annually for repairs and upkeep.

6. Failing to budget for property taxes.
Property taxes — and the likelihood that they’ll climb over the course of your time in the house — should be factored into any home buying budget, says Baehr. To get an idea of how much you’ll be paying, call the local assessor’s office or talk to people in the neighborhood.

7. Assuming your first offer will get accepted.
As home prices get even more affordable, competition is bound to heat up. “You can’t assume you’ll walk in there, make the offer and get it,” says Clark. Try not to get discouraged if you lose out on the first — or second — house you make an offer on.

8. Skipping the inspection.
Before signing anything, hire a professional inspector, says Justin Lopatin, a mortgage planner with American Street Mortgage Co. The seller isn’t likely to tell you there’s mold in the basement or the walls are poorly insulated. Lopatin advises buyers to find and hire their own inspector — independently of the real-estate agent — to ensure there’s no conflict of interest. (You can find inspection companies in the phone book, or by doing a simple Web search with your ZIP code.)

9. Doing too much too fast.
Some buyers want to make the house their own right away, says Baehr. They overextend themselves on credit to do so, and assume the improvement will pay for itself by increasing the home's value. But that’s not always the case — especially in today's market. Instead, buyers need to exhibit patience and make changes over time.

10. Failing to include a contingency clause in the contract.
A mortgage financing contingency clause protects you if, say, you lose your job and the loan falls through or the appraisal price comes in over the purchase price. Should one of these events occur, the buyer gets back the money he used to secure the property. Without the clause, he can lose that money and still be obligated to buy the house, says Lopatin.