Use an existing wireless router with pfSense
From pfSense Documentation
An existing wireless router, such as a Linksys WRT54G, may be used with pfSense in the following way.
- Give the Wireless Router a LAN IP Address in the same subnet as the pfSense interface it will be plugged into (Likely LAN, maybe OPTx)
- This must be different than the pfSense IP address in that subnet. For example, if the pfSense LAN IP address is 192.168.1.1, give the Wireless Router a LAN IP address of 192.168.1.2.
- Turn OFF DHCP on the Wireless Router
- Connect a cable from the SWITCH or LAN side of the Wireless Router to the proper pfSense interface (LAN or OPTx), or into the same switch as that interface.
- Do not use the INTERNET or WAN port on the Wireless Router.
- If running dd-wrt, tomato, or another third-party firmware that can bridge the WAN port to the others, it may be used in that configuration.
Wireless clients should be able to associate with the AP, and then obtain their IP address/gateway/etc from the pfSense router.