A multilingual site usually gets scoped as a translation job. Somebody quotes a per-word rate, the copy goes out, it comes back, and the pages get duplicated under a new folder. That covers the paragraphs. It does not cover the language switcher, the form labels, the validation messages, the confirmation page, the email that fires after a submission, or the alt text on every image. Those small strings are where a second language usually falls apart, because they live in templates and plugins rather than in the document someone sent to a translator.
The structural decisions come first. Give each language its own path, such as /es/ or /tl/, so a shared link opens in the language the sender meant. Set the lang attribute on every page so screen readers pronounce the text correctly and browsers apply the right spellcheck and hyphenation rules. Label the switcher with each language's own name, Español rather than Spanish, and skip flags, because a flag names a country and languages such as Spanish and English cross many of them.
It helps to look at how a local business has set up its language paths in production. Tingey Injury Law Firm, a Las Vegas personal injury firm, publishes its site in English, Spanish, Thai and Tagalog, with each version under its own path. Readers who build for valley service businesses may find it a useful reference for how a four-language build is organized by URL, and a law firm's site, with long practice pages, an intake form and a phone number, gives that structure plenty to carry. Opening two versions side by side is a quick way to see which parts of a template a translation has to reach.
Script changes the layout work more than most clients expect. Thai is written without spaces between words, so line breaks depend on the browser's word segmentation, and a button sized for an English label can clip or wrap badly. Many Latin display fonts include no Thai glyphs at all, which means the fallback font decides how the page looks unless someone chooses a pairing on purpose. Spanish copy often runs longer than the English it replaces, and a navigation bar that fit on one line at desktop width will wrap. Test every language at phone width with real copy, because the overflow only shows up with the actual words.
The larger cost is ongoing. Every new page, hours change, holiday notice and staff update now has to land in four places, and the English version will always be edited first. A practical guard is a table in the handoff document listing every page and the date each language was last updated, plus a rule that nothing changing a promise, such as office hours or what a form does, ships in English alone. Forms need their own pass as well. Submit a test entry in each language and read exactly what arrives in the inbox, then write down who on the client side reads it and in which language they reply.