It not 2% per day. It can get even to 5% per day. But not every day, only some days.
Let's say btc went from 2000 to 3000 and I'm sure it will go down. I want to sell a few BTC for eth but I don't have enough BTC. So I go and sell some which I don't have(borrowing them). But I'm not the only one, everyone want to sell some btc for a quick profit. So the interest rate can jump from 0.001% per day to 5% per day. Does't matter, I know I'll make a quick buck, I'll pay 5%. I borrow, I sell the bitcoins when is 3000(for 10 eth) and after 2 hours I buy them back for 2400(with 8 eth). You get the money back plus the interest rate(5% per day means 5%/12 for 2 hours) while I get 2 eth.
Normally the interest rate is something like 0.006% for bitcoins and even lower for other coins. If you lend the money you do it for 2 days so yo block the coins for 2 days. The interest rate can go up for a few hours and then it goes back and if you have them already lent you can not profit of that high interest rate.
If you plan to hold some money for a while, you can make 5-10% per year if you're using a lending bot. Otherwise you'll get less than that.
Ok, thanks for explaining, I'm gonna try it out.