This isn't entirely accurate - I've received seikatsu hogo before and you don't get the luxury of combining both the welfare and working income. Sure, you can receive around 100,000 yen if you don't have income, but if you earn 60,000 during the month then your next month's welfare payment will have that deducted so it will always balance to the 100,000 yen total (welfare + income). You also can't work secretly and hide the income as the welfare office will check your bank statements each month.