Welcome, and thank you so much for researching before jumping into anything
I'm very happy that you'll be buying a C&C from the cage store. Most commercial cages are not adequate for guinea pigs, they don't offer nearly enough room.
I agree with foggycreekcavy entirely. I highly recommend adopting a pair of pigs. Along with the places she suggested, you can also check out your local animal shelters, craigslist, and guinea pig groups of FaceBook. I suggest getting at least a 2x4 for a pair of females and a 2x5 for a pair of males. Obviously get a same gendered pair unless one is fixed, to prevent pregnancy.
Here is just a basic run down of some stuff, but it's very basic so please do continue your research.
Guinea Pig Feeding Needs
Each day, every pig needs:
-Unlimited grass hay (timothy, orchard, etc.. there are many options!)
-1 cup of pig safe vegetables, high in vitamin C and low/high in calcium, depending on the pigs age (pigs under 6 months need a lot of calcium, pigs over 6 months need minimum calcium)
-1/8 cup of high quality pellets
-Unlimited water
Keep in mind this is PER pig, so at least double that because pigs are social animals and should have a friend of the same species
If you get young pigs (under 6 months old), they will need an extra source of calcium. This can be done in 1 of 3 ways.
1) Supplement alfalfa hay with your long strand grass hay (1/3 alfalfa to 2/3 grass hay)
2) Feed alfalfa based pellet instead of timothy based pellet
3) Feed vegetables high in calcium (a few strands of parsley daily will do the trick)
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Bedding Options
There are a ton of bedding options. I highly suggest doing pine pellets under fleece, and using pine pellets in the kitchen area. Pine should be kiln dried. Other options include towels or UHaul pads under fleece. You can also use disposable bedding. Cedar is off limits, it can make pigs very ill.
The smaller the cage, the quicker it gets dirty... another reason why "bigger is always better" ^.^
A "kitchen area" is an area separated from the remainder of the cage using some sort of tray. It has to be large enough to fit both your pigs, their hay, the water bottles, and food dishes. You use disposable bedding in this area. Many people have a kitchen area because it helps cut down on mess. It's hard to litter train guinea pigs (it literally just depends on the pig and whether or not they want to take to it), so this is sort of a sneaky way to get around that, because a lot of guinea pigs poop where they eat.
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Vet Care
Guinea pigs are not a pet with a short life span. If taken care of well, they can live up to 10 years.
If they fall ill or get injured, you will not be able to take them to a normal cat and dog vet. They do not have the knowledge or training to properly care for guinea pigs. Guinea pigs are an exotic animal, so you will need to find an cavy-savvy exotics vet specialist. Obviously, like with all animals, medical care is not cheap. Please keep in mind that guinea pigs live for a long time if cared for properly, but you will most likely be visiting a vet AT LEAST once in that time. Guinea pigs are prey animals and hide their illnesses extremely well, as a survival technique. That means that once you start noticing symptoms there is *no* time to wait and you must get your pig to the exotics vet ASAP. There isn't time to lose once you notice symptoms.