I am a stickler for cage cleanliness and there's a few reasons why.
Dragons in captivity can't be compared to dragons "in the wild." Dragons in captivity are controlled by the owner. Feeding, timing of heat and lights, health care, and every aspect of their conditions is controlled by you. We're taking this animal and putting them in a confined space with minimal ventilation. In doing so, we're setting up what are actually ample conditions for a hoard of bacteria to begin multiplying.
Now let's say within those conditions, we have feces on top of feces on top of feces, on top of uneaten salads, maybe a few dead feeders that kicked the bucket, and so forth. You've now made the problem worse by making it even more unsanitary in that confined space. You're now setting up a situation where various types of infections and illnesses have an even greater chance of happening.
I can't stress the importance of daily cleaning and regular disinfecting enough.
I change the paper in each cage daily (or as many times as needed) so that feces never sits for any length of time. Every weekend, cages are disinfected with an appropriate cleaning method. So what's appropriate? I'm glad you asked!
Steam over 165 degrees or ammonia diluted 1:10 with water are the only two things that will kill everything that shouldn't be in your dragon's cage. This means various strains of fungus (yellow fungus isn't the only type of fungus), coccidia, other parasite infestations, and so forth. Contrarry to popular belief, things like vinegar or bleach aren't strong enough to kill coccidia eggs.
I personally use steam. I have a handheld steamer from Walmart. It makes cleaning really easy and is very effective.
Cohabbing dragons is a huge hot button topic in the dragon community. Should you cohab? The plain and simple, easy answer is no. You say, "well I see breeders doing it when they post pictures or videos." There is a huge world of difference between an experienced breeder housing dragons together as opposed to a keeper housing dragons together.
It can be argued that experienced keepers can successfully house dragons together, since they know what to watch for. Quite honestly, if you can't afford a second cage, you shouldn't h ave a second dragon. There. I said it.
The thing is, you can't always watch your dragon's cage 24/7 and you could be missing subtle signs that are significant of issues developing. One dragon eating more, one dragon laying partly on the other dragon, a dragon hiding all the time, a dragon always staying clear of the other and not getting proper food or basking heat due to not wanting to approach the area where the other dragon is, and on and on and on. There are many, many clues that cohab situations aren't working out and by the time some owners notice the signs, the other dragon is already starting to fail.
Seriously -- dragons can turn on each other in a second and cause tail and toe nips or worse. Just house them separately to prevent issues. You can't house two males together anyway, since they're dominant and a male and female will constantly breed when they reach maturity, stressing the female out, which will put her health at risk. Two females don't always get along and its really just not worth the constant stress on one or both of the dragons. They don't "need" company, they don't get lonely so let's not even go there.
Dragons "in the wild" (even though I have wild to captive bred comparisons), come together to breed and that's it. They don't even "stay together" as they travel, after breeding. The mental capacity for emotions and attachment to other animals, including other dragons, is non-existent in dragons. If you want to dispute this fact, please make sure you've researched dragon anatomy and brain capacity in the species first. Its a known fact that the functioning is limited and not advanced in dragons. They're solitary creatures by nature.