Investments.

[Cliff Worthington]

Two things can be done.

Investing in a bank.

Example.

Short Term - You put X amount in for 2 weeks at a low %, between 1 and 5%. Higher is rarer. Fluctuates day by day, different for each character. Money is untouchable during this time, can pull it out early for a fee.

Medium Term - Same as short term, except term is a month. And it fluctuates between 5% and 10%.

Long Term - Same as above, but its 2 months, and fluctuates between 10% and 20%.

And/or a Stock Market type thing.

A list of businesses that you can buy stocks in. Updates every X amount of hours to keep people coming back to get the best deals. Different for each character.