If you qualify, you can get a mortgage preapproval before you start shopping for a home. Note that prequalification and preapproval are different. Prequalification is an estimate of the loan amount based on verbal confirmation of your income and often relies on self-reported details about your personal finances.
A preapproval, on the other hand, offers a precise mortgage amount based on your documents such as bank statements, credit score etc. It's important to remember that this initial approval of your finances is just a first step – your ability to close on your home loan will still depend on passing underwriting, which is a more rigorous vetting process.