Hi Isis
I think when you're just starting out, fresh from college, a job is not only a necessity but it's very valuable experience too. Most of the population works for someone else to make a living, so even if you plan to generate 100% of your income from your own business or passive income at some point in the future you're still going to be dealing with most of the population as your customers so having worked in the real world allows you to relate to them and them to you.
This is more important than it sounds at first and I'll explain why - I've had a business relationship with people before who'd never worked a day in their life, two brothers who'd come straight out of college and started their own web design business using money supplied by their father who was a successful businessman. These two were normal decent human beings in all respects but they had
no idea about the real world, how people expected to be treated, how to treat staff, how to treat contractors, which clients were very bad news and which ones were fine (they got a very high % of bad clients because they had no life experience and simply couldn't tell the good clients from the bad ones). I think they would have done so much better in business and in life in general if they'd had at least one job and known what it felt like to have to get up in the morning to be somewhere, how to treat others with respect, how to control their emotions, etc, but they had never had to do these things in a real-life job situation and so they were clueless and consequently poor businessmen.
All that to say... getting a job at least once can help you connect with the larger population on their terms, some of whom will make up your clients and business associates, and to understand what to expect of them and what's expected of you.
Regarding the question of money I personally think a job is pretty much essential until you've had a chance to become settled in life and see your income ideas reach their potential. Straight out of college I'm guessing you're going to have furniture to buy, a pantry to stock, maybe car payments to make, and of course your rent, electricity, water, food, and - heaven forbid - spending money!
Barring lots of cash for investments, or an existing and heavy-duty source of passive income, you're going to have to work to get the money to pay for your expenses.
Personally I disagree with Steve's post about not getting a job, yes he makes some very valid points and yes there are smarter ways to make money but they're also (generally) a hell of a lot harder. And not having money is NOT fun, in any way shape or form, even when you can afford your living expenses it still sucks to never be able to go out to dinner or the movies, to have to budget for everything, to be constantly checking the bank account. I think it's simply easier to work than to live like that. And you don't have to work full-time either, in your situation you might consider working say 3 days a week and spending another 3 days a week working hard on your business ideas.
I hope that helps! Really I think there are a privileged few who never have to work a day in their life, usually living with their parents until they can get their own business started, but the rest of us have to work and build our business ideas and passive income "on the side". Personally I just think it's the easiest way to do it, it may be a little slow but it sure beats eating 2-minute noodles and having the landlord banging on the door