There are a load of threads on this site that will give you ideas.
Cavy Cages gives a 2 cavy cage as 7.5 sq feet min to 10.5 sq feet preferred (so that's 5'X2') .I've got 2 in a 4'X2' that I feel is too small.But it's only their nightcage.
They like somewhere too hide,sometimes from each other.(Yes you really need 2, they are social animals unlike hamsters)
Hay,plain paper or newspaper if they can't chew it.
Not straw-it can poke their eyes.Or shavings or sawdust- chemicals that can irritate their breathing.(Go back a few months on this thread, there are lots of guinea-pig bedding threads)
Foodwise- pellets with VitC not 'meusli' they are picky and waste alot.It's not balanced because they leave alot.Baby pigs like to sit in their food bowl.
Water-always. A bottle each is good is you can.
Fruit/vegetables- lots of lists that they can't eat.Main ones-onion,potatoes,some garden weeds, careful with spinach, no iceberg lettuce.
They need Vit C in their diet.Herbs are good.Peppers especially red.Tomato.Carrots,parsnip,turnip,celery,dandelions,grass,clover. Not ragwort or buttercup.Bulbs and rhubarb also poisonous. They usually avoid anything toxic, but they can't vomit.
Boy or girl? Personal choice, but if you get girls make sure they are double checked or you'll get piglets if one's a chap,and they breed surprisingly young.
Or you can put a castrated boy with a girl.Or get 2 boys, but make sure they are together right from the start or they fight.2 adult boys can't pair up, but 2 girls potentially can.
And don't under-estimate how long they live ,up to 8 years.And how messy they can be, especially indoors.I clean our indoor night cage daily.The outside one every 3 days completely, daily quick clean.
They cannot tolerate damp or changes in temperature well.If you do put them outside at all, protect from damp and wind.
It seems a shame to keep them in all the time, have you got garden space for a summer run (fox, cat and escape proof) They don't dig like rabbits or climb.
If you do get some, they are the sweetest, cuddliest, greediest, laziest, messiest little creatures you can meet. Enjoy
Are you getting adults or babies? And where from.