When you begin looking for a house, you should also begin looking for all the information and paperwork you'll need to apply for a mortgage.

Here's a checklist of what you'll need and it's extensive -- W2s, pay stubs, bank statements, brokerage statements and more. So it's never too early to start a file and fill it up.

If you apply in person at a bank or mortgage company, plan on taking all of these documents with you. The lender will make copies.

If you arrange your mortgage over the Internet, the lender will provide you with a list of documents to fax or mail in. If you mail them, send copies, not the originals.

When you make the copies, photocopy the backside of any bank or brokerage statements or any other documents that have anything on the back, even if there is nothing "important" there.

Some lenders can be obsessive. If they absolutely insist on seeing "originals," you can get photocopies notarized as "true copies," but it will cost you a few dollars.

Debts and monthly payments

Most loan applications ask you to list all your debts and how much you spend each month on everything from rent or your current mortgage, to credit cards, car loans and utilities.

To prepare for that get a notebook and record how much you owe, monthly payments and account numbers every time a bill arrives in the mail. Don't count on your memory.

You won't have to submit any of those bills, however. The lender will check that information against your credit report, which will not only list all your debts but also show whether or not you're paying your bills on time.

Income from your job

Lenders will want W2s from the last two years as well as the most recent pay stub. If you have more than one job, bring in the W2s and the most recent pay stubs from all of them.

If one of those pay stubs shows 10% or more of your income came from overtime, the lender will probably ask how often you work extra hours. If you routinely boost your pay with overtime, the lender can add that to your base salary when determining your debt-to-income ratio and how big a loan you can qualify for. To show how regularly you work overtime, have five or six pay stubs available showing the extra hours and earnings.

Self-employed income

If you are self-employed, get your last two-year's tax returns, both state and federal. A few lenders will also ask for a year-to-date profit-and-loss statement, but not many. Many lenders will not lend to self-employed people until they have been self-employed for at least two full tax years.

If you have a job and are self-employed, you'll need documentation for both.

Sales commissions

If your income includes commissions from sales, make sure you can explain how the commissions are determined and be able to show where you stand for the year-to-date.

Lenders want to know what your base salary is, and in sales it can be fairly low. If your commissions double, triple or even quadruple that amount every year, the lender can add that to your "base salary" and use that bigger number to determine your debt-to-income ratio and how big a loan you can qualify for.

Unemployment income

If you work in a seasonal field -- agriculture, fishing, tourism -- that includes regular layoffs, your unemployment insurance payments could be counted as part of your regular income.

Most state unemployment checks, like most paycheck stubs, show year-to-date earnings. If they don't, you can request a statement from the agency. You can bring in a check stub, a photocopy of your most recent check, or your bank statement showing the deposit.

Disability income

Lenders will count disability income if you can prove you'll be collecting it for at least three years.

The documentation you'll need depends upon where you live and who you are collecting from; the federal government, a state or agency, or private insurer. But when in doubt, bring in your own personal file of correspondence with the various doctors, insurance companies, or anyone else you are dealing with.

You'll also need to document the amount you are being paid each month with a check stub, a photocopy of your most recent check, or a bank statement showing the deposit.

Child support and alimony

You can count child support and alimony as income if you have the court order mandating the payments and proof that they are actually being made. Since you probably can't get the cancelled checks, make copies of the checks and keep bank statements that show the money has been regularly deposited.

If one of your children is about to turn 18, child support will usually stop and the lender won't allow you to include it on your application. The ages of the children and when the support will stop are normally spelled out in the court order.

Other income

If you receive any other regular income -- pension, survivor's benefits, an annuity, allowance, an annual bonus, Social Security income, stock options, even royalties from software, books or music -- you can count it if you can document it.

Use letters or statements spelling out what you are entitled to as well as check stubs, photocopies of your most recent checks, or your bank statement showing the actual deposits.

If the income comes from another country, you may need to provide a translation of the proof that you bring as well as an explanation if things are done in a way an American lender might not be familiar with.

Assets

If you have CDs, savings accounts, 401ks, stocks, bonds, real estate or anything else of value, you'll need proof of ownership and value.

Statements from a bank or brokerage will normally satisfy lenders about stocks, bonds and monetary holdings. For the rest, you will need deeds and other documentation.

If you own land or other real estate, it is up to the lender to decide if it is worth what you say it is. If you bring in the appraisal from when you bought it, most lenders should be able to determine its current value. After all, they are in the business.

If there have been any unusually large deposits into any of your accounts in the past few months, the lender will often want to know where the money came from.

Veterans

If you are applying for a VA loan, your lender will want to see a certificate from your local Department of Veteran's Affairs office proving that you qualify.

If you are currently in the service -- either on active duty or in the reserves -- you will need your military ID and records to show to VA.

If you are a veteran, you will need a copy of your honorable discharge papers. For information about the specific service requirements, call your local VA office or go to http://www.homeloans.va.gov/.

Down payment assistance

If you are receiving down payment assistance from a non-profit or community-based program or a state or county program ask for the paperwork you'll need for your lender.

If you are getting down payment assistance from a friend or family member, you will need a gift letter from the giver stating that the money is not a loan, but a gift that does not have to be paid back. If it is a loan, it changes your debt-to-income ratio and may make a difference in how much you can borrow.

Homeowners insurance

If you are refinancing an existing loan, you will also need the declaration page of your homeowner's insurance policy. It is from the insurance company and shows the term, the coverage and what the annual premium is.

And finally, don't be surprised if your lender asks to see more. Even after you've pulled together all of this.

By Stef Donev

Interest.com Contributing Editor

Have a question about your finances? Ask us at editors@interest.com.