Step 1:
Create a region with WorldGuard
Step 2:
Place a Sign OUTSIDE THE REGION! (Players can't remove them)
Step 3:
Line 1: [arm-rent]
Line 2: the world of the region. If the region is in the same world it can be let empty
Line 3: the name of the region
Line 4: <the price the region should cost per extend>;<the time the region should be extended per click(you can use "s" for seconds, "m" for minutes, "h" for hours, "d" for days")>;<the maximum time the region can be expanded to(you can use "s" for seconds, "m" for minutes, "h" for hours, "d" for days")>
or an autoprice
Step 4:
You are done. Now players can buy the region.
You can now assign a regionkind to the region if you want, so players can find it easier and you can limitate it better.
Use /arm setregionkind REGIONKIND REGION
You can also mark the region as a Hotel, so players cant remove blocks that they haven't build.
Use /arm sethotel REGION true
You can also deactivate inactivityreset for the region
Use /arm setinactivityreset REGION false
You can also deactivate region restoring, if the region gets automatically resetted.
Use /arm setautorestore REGION false
And much more...