System mechanic — not covered elsewhere

The Roadside Shop

A business does not run out of money because you turned up with forty planks

A randomly-placed structure — one of six generic building kinds the world's landmark generator can place, tagged "Roadside Trader" — that stands in the same spot every time the surrounding area streams back in, the same way trees, rocks and camps do. The building itself existed in the game long before it did anything: this system is specifically what gave it a working till.

Why it exists alongside merchants, not instead of them

Every sale in the game had always gone through a wandering merchant, and merchants can genuinely run out of money to buy with — a real, tracked mechanic with its own lifetime statistic and journal entry. The Roadside Shop deliberately doesn't touch that rule; it belongs to the person, not the building. A shop, the game's own reasoning goes, is a business with a counter and a till and books — it doesn't run dry because someone turned up with forty planks. The two coexist as a genuine choice rather than either one being a strict upgrade over the other:

A merchant pays a better price per item — reputation multiplies their rate — but has a limited purse that can be emptied.
The shop pays a flat, unlimited rate no matter how much you sell it at once, but never pays more for good standing, because it's never met you. Reputation does nothing here.

The price

Nothing new was invented for pricing — the shop reuses the game's own existing sell-value function, just without the guild-reputation multiplier a merchant applies, and at a flat 80% of that unrepped rate: the convenience of an unlimited buyer costs a fifth off the top.

Version history

The Roadside Shop added, directly from the request "add shop buildings that randomly spawn on the map, the player can enter them and sell infinite items there (not limited to a trader cash amount)." Rather than building a second, parallel random-structure system, this reused the "Roadside Trader" building the world generator had already been placing since much earlier — the building existed, nothing let you sell in it, and that gap is what this closes.
Fixed an unlimited money exploit. The starting pickaxe, axe and butter knife are automatically re-granted for free if a fresh character is ever missing one — but the shop's sellable filter didn't originally exclude them, so a player could sell all three, reload the game, receive the free re-grant again, and repeat, generating coin without limit. Worse, it briefly left a character unarmed with no way to fight between the sale and the next reload, since the free re-grant only fires once per game load rather than instantly. Fixed by excluding every item the game hands out for free from the shop's sell list — the same rule was later found to be missing two more free-regranted tools (the build tool and landscaper) and extended to cover those too.
Fixed walking straight through the shop's own stone base. Both the Roadside Shop and the Ink House are built on the same underlying model kit as the game's town houses, whose visible stone plinth is drawn wider on every side than the collision box beneath it — a mismatch already fixed twice elsewhere in the game (once for the world's city buildings, once for ordinary town houses), but the shop and the tattoo parlour used a third, separate code path that had never received the same fix. The result was a visible ring of stone around the base of every shop and ink house in the world with no collision on it at all.

Trivia

The list of items the shop refuses to buy is published as a single shared fact rather than copied into the shop's code a second time — specifically so the wandering merchant's own, separately written sell filter can never quietly drift out of sync with it again, after doing exactly that once.
The building itself predates this whole system by well over a hundred versions — for a long stretch of the game's history, "Roadside Trader" buildings stood on the map doing nothing at all.
The Roadside Shop and the Ink House are two of only three wilderness building kinds that were ever kept once the game's own audit found most of them were just one to three loot crates behind a door, paying out once and then standing as dead scenery forever after. Of roughly 712 such buildings surveyed across the world, only 98 actually do anything today — the rest were removed outright, with the empty ground left exactly as it was rather than backfilled with something else.