Your ITIN and your returns
The IRS issues an Individual Taxpayer Identification Number to someone who needs a taxpayer number for federal tax purposes but is not eligible for a Social Security number, and a person can apply for one regardless of immigration status. A lender wants to see that the number is current and that returns have been filed under it. An ITIN can expire, and the IRS renews it; if yours has lapsed, renewing it comes before anything else. Bring the IRS notice that assigned the number and the returns you have filed.
Income, documented
This is a loan on a home you will live in, so federal rules require the lender to verify that you can repay it, and no ITIN lender can skip that. What changes is how. Wages are shown with pay records and the returns filed under your ITIN. Self-employment is shown with those returns, or with a run of bank statements at a lender that reads deposits when the returns understate what you take home.
Credit
A lender reads your credit history the way it reads any other. The federal rule does not set a minimum score; each lender does. Where the file is thin, the same rule lets a lender look at rent and utility payment history instead, though no lender is required to.
What you bring to closing
More is asked of you up front than an agency loan would ask, and the money has to be traceable: statements that show where it has been and where it came from. Whether money from family can be used, and with what paperwork, is each lender's rule. What is left after closing matters here as it does on any lender-held loan, so tell us what you will have left, not only what you will spend.
Where it is not the answer
If you have a Social Security number, or can get one, an ITIN loan may be the wrong loan: with a Social Security number and a residency status the agency rules accept, FHA or a conventional loan may cost you less than this one. Some ITIN files reach a conventional loan as they stand, under Fannie Mae's rules on residency and documentation. The IRS also says you cannot hold both numbers; once you have a Social Security number you stop using the ITIN. If you have only an ITIN today and expect a Social Security number later, this loan can still be the way in, and refinancing into an agency loan once you qualify may be possible.