Building a RF trans and rec. help

Hey, I wanted to build a simple rf reciever and transmitter. I looked on search engines and couln't find any instructions on building them? Can someone tell me the basic parts I would need? I just want to build a simple one to turn a relay on and off. So what my goal is, is having a transmitter on a breadboard connected to the arduino and a reciever on my relay board that I built to turn it on and off. I would use a attiny on the relay board to take the input in and use it to supply the 3.3v to the base of the transistor that turns my relay on? Any advice or a shove in the right direction would be appreciated!

There are lots you can buy for $3-5 on ebay.