Also, there has been some misinformation floating around on these forums, so I'll clear it up: money you borrow (for investment) is considered by the IRS as a cost of investment, similar to broker commissions and margin interest. Whether you borrow from LendingClub, a 0% APR balance transfer, or from your uncle, you can deduct the interest straight from your investment revenue.
Just make sure you keep detailed records of your transactions (cash trail from the borrowing source to your investment account), so you can prove to the IRS that you borrowed the money for investment purposes. Also, try to keep the accounts separate (i.e. don't do a 0% APR balance transfer on a credit card you actively use for everyday purchases).