Arbitrage Opportunities

So, interest rates may soon drop to 0%.

This creates an interesting opportunity.

Let's imagine two people:

Person A: Has a mortgage at a fixed rate of interest (say 6%)

Person B: Has some money to save.

If the savings rates on offer are low - say 2% - it would benefit person B to lend the money to person A instead.

Person A could offset this money against their mortgage and avoid paying the 6% interest charge on that money.  They could, therefore, afford to pay person B a competitive rate of interest - perhaps 4% - and still come out ahead.   One might imagine that there could be lots of people like Person "A" out there (mentioning no names...). I'm sure they'd be interested in such a scheme.

There are three problems, all of them solvable:

1) Person B is likely to be liable for tax on this income so interest rates may have to fall quite far for it to be an attractive deal

2) Person B will worry about the possibility of default by Person A

3) Persons A and B have to find each other.

Problems 2) and 3) could be solved by the introduction of some sort of intermediary. Let's call it a bank.

The bank will wrap up the default risk with their fee for providing the matching service and other administration and capture it as a spread between the rate they'd pay to person B and the rate they'd expect from person A.

So this idea would actually only work if rates fell so far that unsecured bank *lending* rates fell below 6%.

Does anybody see that happening any time soon?