You pay a borrow fee to short stocks. Usually it's pretty low, but it adjusts based on supply and demand.
Today it was 53% (annualized) on Interactive Brokers, and I wouldn't be surprised if it goes higher tomorrow.
(The borrow fee for NKLA briefly hit 900% last summer.)
You can also do a synthetic short by selling a call and buying a put (for the same strike and expiration).
If you look at the implied price from options, lots of people are already doing this (and so you can't get the returns it looks like you'd get from shorting the stock).
