If your parents pay your rent, fund an office rental and you also have an allowance, maybe income from a trust (wild fantasy stuff for me but I went to college with people who has trusts from their grandparents which paid out a few grand a month) then Youtube+Merch is all play money for travel.
Sadly, (because I am an old dreamer at heart) just about everyone I knew with a cool job when I was living in London (writing, acting, musician, interior design, artist) had family money, inheritance and parents bought them property/paid rent. Sure there are a few exceptions but they proved the rule.
The ones who seem very modest and average Joe could also have a paid off house, an inheritance or credit cards and credit union. Like Mark I know people in debt they'll never get out of. They just pay the minimums and don't think about it too much. It's all holidays, clothes and 'Christmases'
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My own holidays are funded with painstaking saving. Every pay day I transfer money into savings. It's small and steady and I hope that I won't need car repairs or a root canal or some flipping thing that will set me back. There's no amount of skipping coffees that will suddenly transfer 000s into my account. That's why I do gasp sometimes at what some of them call a budget trip (usually their 5th of the year) Can't imagine how long it would take most families to save for one let alone those 'cheeky upgrades' that cost a week wages per person