Giving freelancing a shot. When starting small, which expenses and time investments are REALLY necessary from day 0?

I've been freelancing for a few weeks after leaving my 9-to-5 web development job. I feel like I'm where I should be in terms of adjusting to being my own boss and getting enough work going. However, I'm aware of a lot of things which require significant time to set up, or significant startup costs which I'd rather pay once sure I'm in this for the long term:

• Full portfolio site & serious branding process
• Consulting with tax/accounting professionals about the best organizational structure and financial practices for my situation
• Setting up separate accounts and records for work and personal purposes
• Insurance for personal and business needs (I'm covered under my parents' health insurance for a couple more years, which really helps)
• Deciding between paying for a bigger apartment with space for a home office, or paying for an offsite office (like a coworking space).

If I knew I wanted to be a freelancer long-term, all this stuff would be obvious stuff to plan for. But right now I see a lot of these things as potentially inefficient uses of my time and money when I'm still figuring out whether I like the freelance lifestyle.

What kind of things can I not afford to put off in the name of spending more time billing clients? Also, for some of the stuff involving paying professionals for tax, accounting, or legal advice and services, are there any low-cost ways of getting started without paying as if I were starting a huge, official business?