if it's an easy to short stock, none. if your broker has to get a borrow/locate, it depends on the stock, and your clearing firm's/broker's charges for getting a locate.
so if I don't do any margin, then the cost is just the brokerage fee same as buying a stock in intraday time range? Only holding at least 1 day then I need to pay interest for short?
no. if you're not daytrading, it throws a lot of other situations into the mix. and your first question isn't what i answered. you'll need to call your brokerage, because each one handles the situation differently.
You need to have a margin account to short stock. Technically you're always using margin when you sell a stock short, but you can limit your position size to less than or equal to the cash value of your account if you want to avoid being leveraged. Most retail brokers charge ~10% annual margin interest to sell short, prorated daily. So if you're shorting stocks intraday the margin interest should be negligible.
You need to ask your broker. It would NOT be typical to charge for a locate, only for a borrow. They don't borrow the stock unless you have a short position at EOD. 1245