Do all mortgage brokers use the same lenders?

Largely yes at the core, with real differences at the edges, and the person matters more than the menu. The largest wholesale lender is also one of the largest mortgage lenders in the country overall, and the vast majority of brokers are approved to work with them, so there is a lot of overlap broker to broker. Most brokers are approved with dozens of lenders and lean on a handful, roughly five to seven, for everyday loans, keeping the rest for niche situations like non-QM or specialty programs. Pricing and experience still vary a lot between brokers drawing from the same well. As a general rule, a broker shopping multiple investors on your behalf tends to help you. At the same time, a weak broker is somewhat more common than a weak direct lender, since large direct lenders are corporate enough that they will not tolerate someone damaging the brand. The best brokers are usually the best overall option; a below-average broker can be worse than a direct lender. So compare the actual rate, the costs, and how well the person communicates, rather than assuming every broker pulls from a different well or that any two brokers will price the same file alike.