This joke ad would play with the ideas of a loan shark, and the expression of something expensive costing "an arm and a leg".
So the competing mortgage lender is shown as a loan shark, literally a great white shark in a business suit, and as the loan costs the customer "an arm and a leg", the shark literally bites off the customer's arm and leg and eats them. Then the announcer talks about how the company the commercial is for is much nicer to their clients, and won't charge them an arm or a leg, but rather, they charge a fixed rate of (whatever) percent, etc.
