The more documentation you can have ready prior to applying for a loan the easier it will be to process. Your last 2 years W-2s or 1099, 2 years tax returns, last 2 bank statements, last 4 weeks worth of pay stubs and statements of accounts such as 401K or money market accounts would be a good start. Also when you loan officer ask you for additional documentation, that faster you can obtain this and get it to your loan officer the faster the whole process will be.
Because much of the loan process consists of the underwriting process it is important to get all documents in to your agent as soon as possible, so that the underwriter has everything they need to approve your loan in an expediant manner. By providing accurate information about your income, assets, and the necessary supporting documents at the initial application, you will get a fast loan commitment from the investor with little to no prior-to-settlement conditions.
Depending on your unique application, the complete loan process can be finished within as little as two weeks or less.