Since running away from my parents' home and having to arrange living for my first time out of my own means, I've learned a lot and want to share some advice for other young adults. (This article is mostly aimed at Twitter friends; I know a lot for whom doing this could be a reasonable decision in the near future.)
Documents and essential assets
You're immeasurably disadvantaged without government photo ID such as as a driver's license, non-driver state ID or passport. Without one of these, you pretty much can't get a job or housing. Passport is the best; as far as I know it works for anything and applies country-wide. If possible, also have a social security card, birth certificate, and any other legal documents you can get access to.
As much as I hate to say this, and believe me I hate to because phones are an abomination and should die in a fire, it's a borderline requirement to own a phone. Any time you apply for a job or housing, they expect a phone number, and a lot of web forms require you to input one.
A bank account and debit or credit card are extremely valuable assets compared to toting cash around everywhere. A lot of card processing machines will ask you for a PIN; if you don't have one, just try to enter an empty one and that usually works.
Obviously, you'll be renting. And you'll probably have to tolerate housemates.
A big bummer is that unless you have significant income and a good credit score, which you almost certainly don't if your position is anything like mine, you can't rent an apartment traditionally. They have application processes covered in some sticky red substance and usually require you to prove your income is 3x the rent. So searching on websites like zillow and hotpads is a waste of time. Your only options are alternative renting platforms like airbnb.
Some people say airbnb gives worse prices than traditional rent. I think that's bullshit: airbnbs nearly always include all utilities (running water, temperature control, electricity, WiFi) while traditional apartments usually include at most 2 of them and the rest are further expenses. I don't think airbnbs are actually a worse deal when you factor all that in.
Although airbnb is the most well-known alternative renting platform, there are several others.
Hotels are only an option for very short stays because they're about $100/night. That said, if you get caught unprepared and you can afford it, look for one because they're the only option where you can just walk in and get a room without any application process.
Rent (even if it doesn't include utilities) will take the vast majority of your budget. Food will probably be less than 1/4th as much as your rent. Assuming you accept housemates, expect to end up paying about $1000/month for your housing. Much more than that if you insist on not having housemates.
Also, get used to not getting a response. This is worse in the traditional rent system, but even on alternative platforms a lot of places will never respond to your initial inquiry. If you need to ask questions before reserving (and you probably do because a lot of listings leave major ambiguities about what's being offered), reach out to several options.
Finally, don't wait. This probably seems like obvious advice but I got screwed over a couple times by thinking I could put off the commitment for a few days to make sure I didn't find a better option. I couldn't. You can't; reserve as soon as you have a good option.
Tip about airbnb in particular: a lot of places give massive discounts if you book a month or longer, sometimes more than 50%. Another tip about airbnb: just because the airbnb form says your dates are available does not mean they are. Sometimes the form is wrong.
Your residence should be within walking distance of at least one grocery store. When buying food, spend a minute looking for altneratives to each item, because often there are very similar products with wildly different ratios of value to substance. There are a lot of good articles on the web about which foods are the cheapest and how to prepare them. If you shop well, you should be able to feed one person on $5 per day.
When reading nutrition facts, always check the serving size and the number of servings included.
In my experience, delis usually have worse prices than large grocery stores. Don't pay $5 for 2 liters of juice; a supermarket probably sells it for half that. Some delis also don't support card payment, only cash.
And don't even think about restaurants, the prices are absolutely celestial compared to grocery stores.