Not at all! Many of us have had jobs or entire careers in which we helped people and/or made them happy. It's just useful for you to know that those are the kinds of jobs you've enjoyed the most.
You share that risk for homelessness with probably 200 million other Americans.
I'm guessing your brother wants what's best for you. Barista is a very transportable job these days; you can be one in pretty much any city of size. That's good. What's not so good is that it doesn't pay that well (unless tips from customers make a big difference for you). But lots of us got by in low-paying jobs if they met our expenses (and/or left enough time for us to work a second job or "side hustle"). Your brother is correct in that the owner of Coffee-Bean could close the store tomorrow. But the owner could do that even if you were an assistant manager or even the manager. That's a reason to be prepared financially. That may mean that you find another job that provides the majority of your income and your second job/side hustle is being a barista if you really enjoy it. That minimizes disaster in case the store closes and you and your fellow coworkers are all out looking for whatever barista openings exist near you.
I'm familiar with calculus, too, having spent some time in engineering school. Gotta say, in 30 years of working in IT, I rarely had use for it. But some areas of IT would. Support isn't likely one of them.
You would do yourself a favor by exploring more about computer support jobs. In my experience doing them, multi-tasking was essential. And, in a work environment in which your performance is rated by things like the number of tickets you open and close, time management is an important skill. If you cannot develop those skills, you probably should consider a different line of work.
It's easiest if you've managed to save up enough money to cover what you're likely to spend for a few months there: rent (including things like deposits on a room or apartment and the inevitable Target or Walmart run for things like dish soap and toilet paper), food, a phone, getting around (bus/Uber fare/bike/whatever), etc.
Many people renting apartments will require you to pay a month or two of rent up front as proof you won't just disappear on them -- and a security deposit, too. You'll get all that back in almost every situation, but it usually comes to many hundreds of dollars -- a shock to those just starting out on their own. You might want to wait on the apartment until you get a job so you can keep the commute manageable. To be frank, the kinds of jobs you're looking for right now are not the kind that hire people long-distance. You go to the place of work and fill out an application and wait. So being there is important, but, if you can help it, you don't want to commit yourself to picking an apartment and then commuting across town for your work because that just chews up your money and your time. If you know someone in a city in which you're interested, you could see about borrowing their couch for a week or two until you get work and know where you'll want to stay. That might help guide you to cities outside Los Angeles.
So, as iris lilies suggests, your best bet may be to live at home for a while, offering to pay your parents something toward your expenses, and saving as much as you can. Research jobs you might like to pursue as careers. Read up on those fields. Read the Web sites of newspapers in areas you might be interested in living. You can find walkable communities all over the country, though they're much cheaper either in the South or the Midwest. If you're thinking of going to school for either more vocational training or even a degree, use this time to figure out how you can pay for that and how having a certificate or degree might improve your chances to get the job you want.
You're really starting at a very basic level. Nothing wrong with that, either. But you have a few steps to take before you can fly.