To get money you can:

-Search on the ground for those sparkly things and sometimes it's money that you get. They don't give you a lot, but money's money.

-Sell things to Olivia, like furniture and portable items.

-Play mini games, like paragliding, scuba diving, dowsing, racquetball, etc...

-Help tourists. For me, it's the easiest way because once you help a couple tourists, more keep coming and there are a lot in each area and if you help everyone (which will take A LONG TIME) you'll get SO much money! It may take a while, but it's worth it because they give you lots of money.