Seljuks funded caravanserais with permanent endowments

Merchant caravans crossing Seljuk territory along Silk Road trade routes faced days of exposed travel between cities, vulnerable to weather, bandits, and simple exhaustion, with no guarantee of safe, affordable shelter at the end of a day's journey. A ruler wanting to secure that trade route's safety and prosperity had the obvious option of taxing merchants directly for the service, or funding inns and way-stations out of the state treasury year to year.

Both approaches carried the same weakness: a toll discouraged the very trade the infrastructure existed to support, and treasury funding lived or died with the priorities, solvency, and survival of whichever ruler currently held power — infrastructure a trade route depended on for generations could vanish with one change of dynasty or one bad year for the state's finances.

Wealthy Seljuk patrons, often the sultan himself, funded caravanserais — fortified inns spaced roughly 30-40 kilometers apart, a single day's caravan journey — not from the state treasury but through waqf, a permanent Islamic charitable endowment: a one-time capital gift whose income was legally locked to maintaining that specific institution forever, independent of whoever currently ruled.

Funded each caravanserai once via waqf, a permanent endowment whose income was legally locked to that inn forever, so upkeep continued regardless of rulers.

Waqf legally separated funds from rulers, so funding survived dynasties.

Endowment income covered costs, so no toll discouraged trade.

Regular spacing created a reliable network merchants could plan around.

Legal permanence let inns outlive the state that built them.

Capitalize permanent infrastructure into a self-sustaining, purpose-locked endowment instead of annual budgets or user fees.

Nearly a hundred monumental caravanserai complexes were built across Seljuk and later Ottoman territory on this model, creating a continuous, reliably-spaced network merchants could rely on regardless of which dynasty currently governed a given stretch of road.