I don't think the problem is a $4 latte either, but it is at the same time, as there's a knock on effect. $4 here and there soon compounds to $500 on little things that don't matter. I do think there isn't enough focus on increasing income on this forum by working side jobs/becoming self employed. I find the article about jobs that make more than $50k a month far more important than most on this site.
You're right that it doesn't come up explicitly in a lot of threads. But functionally, there's very little difference between a side hustle and insourcing things most people hire out. I would argue that the latter is just an easier version of the former - you took an easy job you were paying someone else for, and now you're "paying yourself" to do it instead. Once you've insourced all the low-hanging fruit, only then does it make much sense to leave your house for a side job.
I'm not knocking the side hustle BTW, because in addition to all-DIY all the time, I have
three side jobs and they are truly the key to my future. They provide me with variety, new friends, new skills, real enjoyment, extra savings, and by replacing part of my full-time income they'll speed FI along by several years. But I honestly don't feel like there's much to say about them. Work is work, pay is pay, get what you can, and it all goes in the pile ('stash). MMM's stance is that increasing your income is great, but we generally have more power over our SR than anything else; hence, his focus thereon.
Side note:
I make my own espresso at home, not just for the 90% cost savings, but also because I do it
better, and in
less time than it would take to drive to a cafe' and sit in line for one. Fuck that noise!
