It depends on what accounting system you are using. If you are using a cash basis, you claim the expense when you pay for it and the net income would be your revenue minus your expense.
On a cash basis, your net income would be $200, $1,800 in revenue less $1,600 in expenses.
If you using the accrual basis, there really isn't enough information to tell you what your net income is. Revenue is recorded when it is earned, not when it is received. Under an accrual accounting system, the $800 paper purchase would go in as an asset, and then as you use the paper it would be written off as an expense. and this doesn't include any labor expenses.
Just on the information you have given, under an accrual accounting system:
Revenue: $1,800
Expenses: $1,000
Net Income: $800
Assets: Cash on Hand: $5,200 (start up cash plus net cash flow)
Paper stock: $600
It would be a good idea to find a bookkeeper or a CPA to set up an accounting system for you. All of this can be automatically generated from any accounting program (Quickbooks, Quicken, MS Money, etc) if it is set up properly.