To pre-qualify is to earn the right to something before the time comes to attempt to actually gain access to or possession of the thing. Pre-qualification is commonly used in banking to determine which borrowers are eligible for loans or for certain properties of loans based on conditions that exist before the borrower even applies for the loan.
An example of someone who pre-qualifies for a mortgage loan would be a man who is making $150,000.00 per year and has a credit score over a certain number and is approved by a financial institution to receive the loan. In this case, the bank may simply pre-qualify candidates for the loan based on financial criteria such as these. People who prequalify for things, including loans or credit cards, often automatically earn the right to choose whether or not they would like to accept them. This is in contrast to people who do not qualify in advance, and must fill out applications to see if they qualify.