At the height of the lending boom, you could be zero for three -- lousy credit scores, little or no down payment and unable to prove your income -- and still get a loan. Today, "you better be two for three," LendingTree.com's Svinth said. Good scores, a down payment of 10% or more and a steady, provable income put you in the best position to get a loan.

The requirements for credit scores have changed the most significantly.

FICO credit scores range from 300 to 850. Mortgage lenders typically pull borrowers' scores from each of the three major credit bureaus -- Equifax, Experian and TransUnion -- and base their rates and terms on the middle of the three scores.

In the past, FICO credit scores of 620 and below were considered subprime, which meant getting a loan would be more difficult and expensive. At the height of the boom, some lenders lowered that bar to 580.

Today, 660 is often considered subprime, and any score below 680 is likely to result in higher rates and tougher terms.

"If you have mediocre credit, you better have a 10% down payment," said Dick LePre, a senior loan consultant for Residential Pacific Mortgage, who writes a weekly on the mortgage business. LePre defined "mediocre" as scores between 640 and 680.

A year ago, you didn't need any down payment to swing a home purchase. Today, only a few lenders offer 100% financing, and you need sterling scores and solid income to get those deals. Otherwise, 5% down payments are typically the minimum required.

Factors you don't control

The final piece of the puzzle is the appraisal. Once accused of inflating valuations to appease buyers and lenders,  a home's potential value.

Matt Hackett, Equity Now's underwriting manager, said many deals are threatened and some fall through when the appraisals come in too low or an investor rejects the appraisal because the "comps" -- sales of comparable properties used to evaluate the home -- are more than 3 months old.

"In a lot of these areas, homes are sitting on the market for six months at least," Hackett said. "There are no comparable sales within three or four months."

There's also the issue of the "haircut."

In certain declining markets, mortgage experts said, Fannie and Freddie chop 5% off the amount they will lend on a house.

If the appraisal on the home you want to buy is $300,000 and you have a 10% down payment, for example, you'd normally get a loan for 90%, or $270,000. In declining counties, though, Fannie and Freddie instead will lend you 85% of the appraised price, or $255,000.

You either have to come up with extra cash, Svinth said, or arrange a secondary loan in these areas (mostly in California, Arizona, Nevada and Florida).

Before you make the leap

Given the state home markets are in and based on input from these experts, here's my best advice for potential home buyers today:

• Consider waiting. I'm not a fan of trying to time any market, but buying as real-estate prices are still falling takes a special kind of guts. If you're prepared for your home to continue losing value, your finances are in great shape and you plan to stay put for several years, you can go ahead and buy. In most markets, though, there's little penalty for waiting until prices start to recover, especially if you use the time to build your down payment and improve your credit scores. If you could benefit from the higher caps on home loans, that's an extra reason to put off buying until Congress acts.

• Whip home value report those credit scores into shape. Read "ers. If your scores are good but could be better, consider paying down credit card debt and not using more than 10% of your cards' limits at any given time. It's particularly important not to open or close accounts when you're trying to improve your scores.

• Build your down payment. The more cash you can bring to the table, the better the loan you'll secure. Shoot for 5% as your minimum, but 10% is even better, and 20% is great if you can swing it.

• Identify your reserves. Lenders like to see that you'll still have money left over after making your down payment; that gives them a comfort level that you'll be able to cover your mortgage payments even if you suffer a temporary setback. Cash in a savings or money market account is good, but so is cash value in a life insurance policy or investments in a nonretirement account you could easily sell. You don't necessarily need to turn these resources into cash by borrowing or selling, but you should include them among your assets when filling out mortgage applications.

• Work with an experienced loan officer or broker. The mortgage lending situation right now is changeable and sometimes chaotic, so you'd be smart to have an experienced hand guide you through the process. Ask for referrals from friends and others you trust.