margin lending interest, page-7

When you are using an instrument on margin (CFD's, futures, etc.) it is generally like this.
At the end of the business day they will calculate the total position size (margin does NOT offset this) and charge it daily at whatever the going rate is.
Generally cash rate (in country of country of contract) +/- (long/short) 2.5-3% fee.
So yes its possible to short a stock in a country with a low interest rate and end up paying for your provider to hold the cash for you!

If positions are open and closed during the business day then generally no interest is charged.

If your talking about forex and hold the position over night then you will be charged tommorrow/next rate which is the difference between the interest paid on the currency you bought and the interest received on the shorted currency, again if you close the position during the hours of trade then no interest is charged.