A good omni antenna strapped to a chimney or a pole (which can be secured to the roof, wall or vent pipe will get you started. As you add subscribers, you will want to go to add APs and use sectorized antennas to increase capacity.
We can help you with a complete spec (mounts, range, cabling, etc.) if you want.
Be aware - Cable companies have started to cut off subscribers who use their Cable Modems to grant access to others via wireless. If they know about it.
Matthew Wheeler
Chief Wireless Architect
www.BlueModal.com