Cheat: Infinite Work Days/Yen
As beloved as Shenmue is, we couldn't rank this cheat higher because it involves working a tedious warehouse job. But you're addicted to the local arcade and gumball machine prizes, so at least this job will teach you the value of money (sorta).
If you play the game correctly, you'll only need to work several days in order to move the story along. Though if you want more money, here's how to keep working as long as you like. On your third day on the job, you're supposed to investigate Warehouse #17 after work. Instead, skip this event and the next day you'll repeat this third day on the job, just with a bit more money in your pocket. Repeat this as many times as you like.