What actually stops when the system does
A restaurant with a dead POS takes cash and hand-written tickets and loses card sales, its inventory counts and its tips reporting for as long as it lasts. A shop with a dead server loses its scheduling, its invoicing and, if the backups were on the same machine, its history. The hardware is a few thousand dollars. The days without it are the expensive part, and the first call is whoever can get a temporary terminal or a laptop running today — most POS vendors will overnight a replacement to an existing account.
The hardware and the software: equipment
Terminals, tablets and stands, a receipt printer and cash drawer, a back-office server, the network switch and access points, the workstations: these are assets with serial numbers, and equipment lenders finance them over two to five years with the vendor paid directly. Many POS vendors run their own financing or a subscription that bundles the hardware, and that is often the fastest route to a working counter — read the contract for the term and the early-exit terms before signing on a bad day.
A newer business or a thin file is asked for a down payment. The amounts are small enough that this is rarely a hard approval.
The recovery: working capital
The IT contractor's hours to rebuild, the data recovery service if the backups failed, the staff hours re-entering a week of tickets, and the sales lost while the counter was cash-only are not assets. A working capital loan or a cash advance on your last three to six months of deposits covers them, decided in about a day and funded in one to three business days. Borrow the invoices, not a round number, and ask for weekly payments.
If it was ransomware
A locked system with a ransom note is an insurance event and possibly a legal one before it is a financing one. Cyber coverage, if you have it, usually requires notice within days and has a panel of responders; paying the ransom from an advance without talking to them can void the coverage and does not reliably get the data back. Call the insurer, then a professional, and then decide. The funding above covers the rebuild either way.