Make a mission that shows up if the player has enough money. Have the mission invisible, and make it auto-aborting and set a bit. Make it so the mission starts automatically unless that bit is set.
Make a cron that runs every day, checks if the bit is set. If the bit is set, unset it. If the bit is not set, trigger a second mission which will be the "give player money" mission. The "give player money" mission unsets the "has money" bit so the "do you have money?" mission can run again.
Something like that. Note that this will cause problems if the player loses money in space, has no fuel to jump (triggering the check-money mission and cron), and cannot land without paying a fee that he can't pay.\
This may work well in concurrence with the "make time pass in space" method of incrementing the clock without landing or jumping.
This post has been edited by LNSU : 08 November 2010 - 11:51 AM