I would open up a business bank account and get a business credit card, and be very meticulous about keeping your personal/business stuff separate. Also, keep good accounts (receipts, bookkeeping, etc)!
You can get an EIN in about 5 minutes online.
Normally your equipment will have to be depreciated over 5 or 7 years (depending on what it is), but under
Section 179, if you purchased the item new you might be able to expense it upfront. Although I hate paying extra for someone to do my taxes, I found all this stuff very complicated and got a professional do my taxes (the software is called "Quickbooks", by a company called "Intuit"-- how complicated could it possibly be? Turns out, very-- though there are simpler options than Quickbooks out there). A CPA can also help you figure out what you can legitimately expense, and with tax-optimized planning if you need to buy more equipment in the future.
An LLC keeps your business assets completely separate from personal, so if you get sued they can only go after your business assets and not your private assets. Not sure what kind of business you're looking into, but if there's any potential in being sued I'd definitely get the appropriate insurance to cover it! When I had my wedding photography studio, it was worth it for my peace of mind to pay the extra $100/year to have it as an LLC-- you never know what can go wrong.
Also, do be careful about whether you're running a hobby business or a for-profit business as defined by the IRS. If it's a hobby business, you'll only be able to deduct up to the amount of income that you generated.
Good luck!