Is there an online ordering system free to start with, or do I pay before my first order?

You start free. The trial is 15 days of the full product, up to 1,000 orders, and no card is asked for. Your ordering page, your menu, WhatsApp messages, stock and reports are all there from the first minute. After the trial you choose a plan under Settings → Plan & billing, and if you do nothing the page pauses and your data waits for seven more days. An online ordering system free for 15 days is enough to take real orders and decide. The Account, trial & billing tab in the docs explains what the trial includes.