freqtrade_origin/docs/leverage.md

An instance of a Trade/LocalTrade object is given either a value for leverage or a value for borrowed, but not both, on instantiation/update with a short/long.

• If given a value for leverage, then the amount value of the Trade/Local object is multiplied by the leverage value to obtain the new value for amount. The borrowed value is also calculated from the amount and leverage value
• If given a value for borrowed, then the leverage value is calculated from borrowed and amount

For shorts, the currency which pays the interest fee for the borrowed currency is purchased at the same time of the closing trade (This means that the amount purchased in short closing trades is greater than the amount sold in short opening trades).

For longs, the currency which pays the interest fee for the borrowed will already be owned by the user and does not need to be purchased

The interest fee is paid following the closing trade, or simultaneously depending on the exchange