OP wrote:
"My computer will be in my room and there's no hard connection to the internet so I'll be using wifi. Would I need like a Airport for my computer?"
My opinion is that for a desktop, WIRED ethernet is ALWAYS better if you can use it.
Is there any way to string ethernet to where the iMac will be?
If you need to buy a wifi router, I consider the Apple Airport Extreme a good buy, simply because of the ease of setup.
Be aware that you can get these as "Apple-refurbished" units for about $129 from the refurbished section of the Apple store.
Tell us about the current ISP service in your house...