In my (small) hostel we just use basic computer equipment. The reception uses a laptop, and we have one tower unit for a guest computer. Internet runs with a cable modem and a wireless router. Nothing special. We don't need secure servers for credit card numbers because we don't store them.
For your wireless routers, The number you would need for 6,000ft2 (550m2) depends a lot on the shape of your building and how thick the walls are. If your property is split on several levels, you would probably need at least one router on each floor.