Definitely keep a separate account for your business expenses. It makes accounting MUCH easier. Keep all business related receipts (so you can deduct them later). You've got to treat it like a full-blown business (because it is one
)
Now, since you're making > 600 per quarter (or will be), make sure you withhold on yourself 25% of your
profit so that each quarter you can file to the IRS those withholdings. Most small business really teeter on the edge or go under b/c they don't keep up on their taxes.
If you're also employed, you could increase your withholdings substantially there and file your quarterlies automatically by having the employer do it
That's what I do.