Minimum dimensions are usually suggested to be 2x2x3'. Ferret nations, especially doubles, are the most popular but many ferret cages and large aviaries can work. You will have to fill it with wood shelves and remove or cover any plastic or wire mesh in fleece. Bass equipment makes pans that fit the ferret and critter nations as well as custom pans for a pretty low price.
Most people just use fleece layers for bedding. Some are just folded over like ours and some actually cut and sew liners with sometimes an absorbent layer of something else in between layers of fleece. You can buy such liners if you want them and don't want to make your own. Other fleece items are used like hammocks, tunnels, hanging houses...
Some chins can be litter box trained to a point but they aren't great about it. Mine rarely pee when out but they do poop everywhere in and out of their cage.
Wheels must be metal with a solid running surface. Silver surfers are the cheapest, then flying saucers-some chins have trouble learning to use them, and then the more expensive wheels like chin spins. The more expensive wheels have their benefits like being quieter, having larger running surfaces, and lasting longer.
Chins don't really bite. Young ones and those just getting used to human interaction may accidentally nip while looking for treats or testing what fingers are but I've never had them break skin. If you really corner them they may bite harder but they give you tons of warning and make every attempt to get away instead of resorting to fighting you. If they run off in to their house don't reach in after them. Mothers with babies are the exception since they may stand their ground guarding their babies instead of avoiding you. So long as you listen to their complaining noises and especially any lunges in your direction by backing off they will not do more than the accidental nips. After about a few months they learn to carefully scrape teeth across your skin until they encounter the treat and then take it. My older ones can take a single grapenut or piece of oatmeal from between my fingers with no discomfort to me.
Most do not like to be held and they tolerate petting to a varying degree. Mostly they want talked to, fed treats, and let run around. They generally aren't very cuddly animals. You do get the odd one that has been handled a ton since it was born and will sit still to be picked up and held for longer than average. Chin safe rooms like bathrooms or large play pens work best to interact with them out of the cage. You can sit in the middle and once they get used to you they will check in for attention and to climb on you between running about the area.
Most chins do benefit from a friend and 2 chins is not really more work than one. There is the risk they may have a falling out though and no longer be able to live together. While most may enjoy a friend they will also usually get along just fine on their own. Some may need an adjustment period if they've never been alone but after awhile they are bouncing around and eating like any other happy chin.
Chins should not have dried fruit or food with little colored bits and such in it. It should be a plain pellet. Oxbow and Mazuri are considered the best. Some feed a pellet called tradition but personally I think it's junk. If nothing else the fact it has animal products in it turns me off from feeding it to a true herbivore. If you can't get those pellets rabbit pellets can work. Most get the kinds sold at feed stores. Nutrena and manna pro/gro/sho are the most popular. They need unlimited good hay. Many buy from kmshayloft.com or oxbowhay.com (you have to follow their retail links since they no longer sell directly) but if you do some searching and research what quality hay looks like you can often find good stuff locally in 50lb bales for between $5-$20 depending on your location. We spend $10/50lbs on organic clover that we use as a supplement and treat to their km's bluegrass and we have a small bag of oxbow oat and oxbow botanical which has herbs in it that we give one handful of something besides bluegrass a week as a treat.
They need lots of chewy toys. Wood especially. We keep a box of small wood pieces next to the hay box and just throw each new wood order in there and take out a handful per cage a day. You can buy all sorts of coins (drilled and not) to put on safe rope or those metal bars with screw on bells and those chains with bells, twigs, perches, ledges, etc... from the vendors on here. Check the banners at the top and the classifieds at the bottom. Some other materials are useful too like loofah chunks, woven willow items, and coconut. Some sell custom made toys and you can use plastic free bird toys. If you buy your own all natural (not anything treated for crafts but stuff with an earthy smell) hemp, jute, or sisal rope and bulk toy parts from chin and parrot sites you can make toys for cheap. Sometimes we also score something interesting on the parrot sites like the 25' grapevine that they spent months destroying.