First of all, I agree with you that banks are in the business of not only making money but also lending. That is where they make their money. They would, in this case, receive interest from the loan as well, so they would make money from it. There are hundreds of options to approach right across the country.
What we have seen in Ontario, which has similar provisions in the sense of getting a loan from a bank, restricting it to financial institutions, is that they have made those decisions based on your rebate. As federal politicians, when we run, we receive a rebate if we get 10% of the vote.
As you said, if a viable candidate is going to receive 10% of the vote—which is well below viable; to be a viable candidate the person would likely receive more—the candidate can guarantee his or her rebate over to the bank. The bank can make that assessment based on the rebate, not based on the person's personal wealth, personal credit, or other personal situations. This would be based on the rebate they would receive.