If you can find a nice cage readily made, I would buy it if your carpentry skills aren't up to par (like mine)... Although, it would be cheaper to make your own cage, probably.
If you're getting a nosy be (or a veiled), it needs to have three screen/mesh sides. Plastic mesh is best, as metal mesh will hurt their claws/nails.
My male Nosy Be cage is made of wood and mesh, and is about 6 feet tall. It has a built in UV light and a heat lamp that sits on top of a metal screen at the top...
Here's a pic (the monkey's name is Eddie):
I have a big fake tree in there, and some hanging live plants with vines...
Good luck!