This is akin to asking: "How much does a car cost?"
The most annoying, yet fitting, answer is: "It depends."
Are you asking about software? Will you be creating and sending invoices? Do you have employees and HR needs? Do you have a website? Need one? Will you be managing IT needs on-site?
Are you asking about hardware? What kind of foosball table? Remote access to the office? Desks and chairs?
I'd love to help, but the question is a bit vague. I'm not sure if any other experts will be able to add much value to your inquiry.
Please add more detail and we can get rockin'