Purchasing a home is not an overnight process. It takes time and preparation. The first step to take is getting pre-approved. Nothing else sends a stronger signal to a seller than getting pre-approved. Many buyers place a lot of emphasis on down payments and credit scores. While these are an important part of the process, getting pre-approved is the best way to start. Here are the things you will need to get pre-approved.

1. Proof of Income: The best way to provide proof of income is using past tax statements. W-2 files are acceptable.
2. Proof of Assets: You need to prove that you own things that are worth money. These are assets. This includes the money in your bank account you will use on the down payment and closing costs.
3. Good Credit: In general, the higher credit scores you have the lower interest you will need to pay.
4. Employment Verification: It turns out that you can’t grow money on a tree in your backyard. You need to hold down a job. You also need proof that you have been holding down a job for the past year or two.
5. Documentation: You need to prove that you are you, and not an imposter. To do this you will need your Social Security number.

Source: https://www.investopedia.com/financial-edge/0411/5-things-you-need-to-be-pre-approved-for-a-mortgage.aspx