Investments aren't taxable. You need to make sure you have proper documentation from your investors showing either their membership interest (LLC), shares (C or S Corp), or other article of organization showing their ownership interest in some way.

You are required to pay taxes on revenues earned, but in many cases you aren't required to pay unless you cross a certain threshold. Each state has its own laws, and you can search "Department of Revenue for [STATE]" in Google and find the best way to record your revenue and taxes.

Once you get enough revenue, hire a firm like ADP to do your payroll processing and also set up the corporate tax payments through them. This makes things easier, but does cost money.

Since you didn't mention how your entity is set up or where you are doing business, it is hard to give specifics.