The ImpulseRC Alien RR5 from Rotor Riot is a proven build kit. Included is the frame and accessories you need to build your own Alien 5". Just add your own electronics and you're good to go.
This kit is a great choice for someone looking to build their first quadcopter. All the small parts that you would have to seek out one-by-one are included here. This combined with a detailed build video (below) take lots of possible heartache out of building something fully custom piece-by-piece.
Also see the original Alien 5" frame.
Alien Frame Specs: