Loan Prequalification
It's hard to talk to an agent anymore without being asked, "Are you prequalified?" Agents are taught from day #1 to push clients to prequalify early in the shopping process. This is for good reason: in order to have an offer seriously considered, it must be accompanied by a loan prequalification. Depending on the lender, this can sometimes take a couple of days to get put together. Therefore, it's helpful to have it from the beginning.
When buyers first talk to a lender, they may find out that they can qualify for a much bigger house than they initially expected. They may find out they can't qualify for what they wanted. This is important information. That said - it's quite common to be approved for a loan larger than you can afford. You should be realistic about how much you can afford, and stay within budget.