what do I need to get a PO BOX for a business?

[GIGI]

If i am starting a business, where the letters and payments would be sent to a PO Box, under the company or site name...what do need to do? like lets say my company or site name is "flower power123" how do i go about getting checks and money orders WRITTEN OR MADE OUT TO flower power 123 and being able to cash them at my bank and receive them at the post office under THAT name rather than my actual birth name? Do i need to do the operating under fictitous name thing, do i need a business license? what do I do