The same plots behave very differently depending on game mode.
Single player
A player pays a fixed price and the land belongs to them forever, without the ability to sell it. It's a one-time investment.
Multiplayer (dedicated server)
Each property is available for rent for a period of time, with both rent timeframe and price adjustable by the server administrator. The Fandom wiki explicitly notes that "multiplayer properties are rented for a real-life week rather than owned so if someone stops playing on the server the property will eventually go up for rent again, preventing the properties from being hogged by inactive players".
Example server timer
Community servers can tune the timer. The ASEAN Motor Club server, for instance, uses a 15-day rental window with a 7-day guaranteed period plus a 3-day grace period to renew. Defaults vary by host.
Related
Both modes share the fast-travel mechanic — see that article for the teleport rules, especially the multiplayer rule allowing teleport to any owned property regardless of who owns it.