Typically, no. On most residential mortgages, the lender pays me a finder's fee when your mortgage closes, so there is no cost to you.
Working with me means I can see rates across lenders and know where I can negotiate the best rate and term. The only time a broker usually charges a fee is on an alternative (B lender) mortgage, and I would tell you what it costs upfront, in the first conversation.
Working with a trusted broker can often save you money over the long run, through good advice, lender deals only available to brokers, and volume discounts some lenders offer.