Just added a cash lottery system to the LMS NPC, she will take 500mil off you and add it to a pot o gold with your name on a list.
Every wednesday 1 random name is picked RANDOMLY at random and will be added to a winners list. When you go back to the NPC she will tell you that you have won and to collect your prize.
Your prize will be relative to the ammount in the pot o gold (of the week that you won (so dont think you can cheat it somehow)) rounded to the nearest 5billion (thats rounded up or down) and paid in scrolls of cheques.

One character can only play once per week but you can use multiple characters to have multiple chances at winning.
If you win you will have unlimited time to collect your money so there is no rush.
You will only find out who has won when the person collects it there will be a red shout by the NPC.

good luck