Surely you don't need to know WHY he wants it, to give advice? He's not asking for counselling on his life choices after all.
It's difficult to respond to "I've booked myself three international holidays but I just don't have enough money" without a little curiosity about the circumstances.
So it is always 'worth it' to have a second job
In terms of making a net monetary gain, yes. But if you're just taking a time filler job at low wage, the actual gain might not be worth the time investment. So not necessarily always "worth" it.
One little caveat in your situation. You said you are in the 40% tax band already with your first job.
Then with a 2nd job I imagine they would put you on BR and tax any income at 20% - but you should be paying 40% on it, so at the end of the year you will owe the 20% extra tax on the 2nd income.
If everything's declared and above board, etc, then HMRC will issue you a second tax code such that you will pay higher rate on the second job via PAYE, there won't be an extra bill at the end of the year. Obviously that's massively dependent on the OP's current tax situation.




