Let's say I have a diversified investment portfolio, and I wish to tap a relatively small amount of cash (less than 5% of the portfolio's value) without liquidating any of my positions.
I could borrow on margin, but rates are presently 6% - 8%, which is unattractive.
Wouldn't it make more sense for me to short-sell treasury bonds instead? With rates below 1% for the shorter-duration bonds, my borrowing costs are much lower (as I understand, I would be paying the interest that the bondholder would ordinarily receive, instead of paying margin interest to the brokerage)?
There is the risk that the bonds would appreciate in value, but given that interest rates are currently about as low as they can go, this would be extremely unlikely (and even so, the change in value would occur very slowly).
Are there any risks/disadvantages that I'm overlooking?