First of all, let's face the facts. Working 9 to 6, you won't have any time during the day. If you choose to have a second job during the evening hours, you'd get burnt out very easily. Chances are that you might under-perform in both the jobs. I recommend having a side business rather than a second job. Some investment of money and time would be required at first. I have come up with a few options that would require less work from you but would be a decent second source of income.
Most of us think of investment income as just the cash flow we get from bank interest, bonds, share dividends and property rents, some of which comes via a super pension. But a more complete view is to also consider how growing the value of your investments can add to your spending potential. This total return approach generates income from both income and growth to optimise spending from your portfolio across all market cycles, aligning cheap and expensive investments to your goals.