I’m generally wondering what non-wealthy people did to lock up their homes without the key-lock combo built into a door, which seems to be a roughly Renaissance-era level of craftsmanship development. Wealthy people, of course, being able to hire someone to watch the place, and buy locks as soon as they were historically available.
Why do you assume that keys and locks are a Renaissance phenomenon? Locks are an ancient phenomenon dating back potentially to the Assyrian Empire, with metal locks and keys being a relatively common find from the Roman Empire. YORYM-AB6E48 and WREX-AAC496 are good examples of Roman keys found in Britain. There's a fairly substantial corpus of Medieval keys as well, such as BERK-C1D46A, DUR-BFD8A9 and PUBLIC-54D2D6. SUR-19FFD0 is part of a medieval copper padlock recovered just last week from near Winchester.