The Reg T initial margin requirement for a short sale is 150%. The first 100% of the it can be satisfied by the proceeds of the short sale, leaving just a 50% actual cash requirement. The maintenance requirement is 125% of the current market value of the short sale. Brokers can require higher amounts of either and they can also have a minimum account size requirement.
You borrow one share of stock A trading at $100 and you sell it. Ignoring commissions, $100 is deposited into your account. You need $50 in cash or marginable securities to support this trade. Each security has a borrow rate. It can be as low as .25% (AMZN or NFLX) or for something rich, today's borrow rate for the cannabis stock TLRY was 175%. This rate is applied to the price of the underlying not the cash proceeds from the sale (you borrowed the share not the cash). It is an annual rate and you are charged each day that the shares are borrowed. It varies from broker to broker. In some cases, the number of shares available for lending is non-existent and you cannot short.
If your broker pays interest on cash balances, you will receive some interest in return since the proceeds from the short sale were deposited into your account.