Wireless IP phone small office system?

Wireless ip phone small office system?

I have a small business that I would like to run VOIP system in but: a) I don’t want to pay thousands of dollars for such system and b) I’m renting an old office space that does not have LAN capabilities and I’m having a hard time negotiating a deal with the property manager.
How would I go about a Wireless ip phone system that would allow me to run my business better and not go through construction, wiring closet, wall ethernet ports, etc
I’ve been looking at some Wireless ip phones but I don’t think it is as simple as turn on a wireless ip phone, connect it to your wireless router, and you are all set. Can someone give me an idea on what other equipments are needed?