Hmmm. You want to do what I did off the bat as an iPhone Noob -- one week's experience so far.
If you don't yet have a router for your house, perhaps using a computer RJ-45 and twisted pair to connect directly to the ISP's modem, -- yes -- you need a router.
How many users and computers in your house? Do you have a laptop with wireless capability?
A decent router is a one-time investment (until outmoded by newer technology and models). I'm still rocking a CISCO E2000, but looking for a replacement that offers simultaneous 2.4 and 5.0 bands. If you're connecting other PCs, you'd want the four (or so) LAN ports to provide gigabit or 10/100/1000 speed, but 10/100 would probably do for now.
I think I paid $80 for my E2000. "Higher end" could mean $140 or more.
A "tech-buddy" of mine tipped me to a NETIS wireless router on sale at the EGG for $15. The ports are only 10/100. We were thinking of using them as wireless access points (which can be done, as JackMDS will tell you). But the 10/100 ports would limit the wireless output.