You should get big storage boxes the clear snap lid kind and drill a hole on the side for water that's what I did.
wood and nails
This is not really a custom cage, but a cage with homemade penthouse on the top. http://www.guinea-pig-paradise.com/homemade-guinea-pig-cages.html
I prefer already built cages over custom built ones as they tend to last longer. I got my guinea pig's cage here http://www.petproductsbyroyal.com/rabbit-guinea-pig/
I try to clean my guinea pig's cage around once a week or when it looks dirty.
no
It means that the guinea pig wants to go back In its cage if not that then the guinea pig is cooled
Guinea pigs don't always make people itch. If they do, then it probably means that you are allergic to the guinea pig, the hay you feed it, or the sheddings in it's cage.
You might see the guinea pig look around the cage and call for it. Whenever I take my guinea pigs apart the one that's still in the cage looks all around the cage and if he doesn't see the other guinea pig he starts squeaking.
It depends. They certainly wont be aggresive, but if you do, make sure to spay and nueter them.
a great place to get a guinea pig cage is probably Amazon or Craigslist.
No, paraketes need a bird cage not something made for a guinea pig. They have special needs for their cage so you need a bird cage.
Depends on the Guinea Pig - also on the cage. I keep my guinea pigs in an open-bottomed cage.
if it gets REALLY REALLY bad possibly. if the cage is pretty dirty,it could make the guinea pig sick or it isn't good for him/her. Most likely it wont kill the guinea pig.