When reading the this question, I wondered how on earth Chandler (and Joey) could afford living where they did. The linked question provides some clue as to why Monica was able to afford hers, but her rent seems to be way lower.
So how were they able to afford living in their apartment?
(Note: I'm not an American so I have a hard time determining whether their living arrangements are realistic.)
Out of universe: cramped environments, unless relevant to the plot, are needlessly obstructive to watch a show/movie. It's a common complaint that living spaces are roomier than the supposed income of the character would allow for.
Chandler is by no means badly paid. His job is boring and specific details are obfuscated because it's part of the joke as it "proves" how boring Chandler's job must be, but it's still a well-paid office job. Consider that Chandler has a private office and an assistant, he should be able to afford an apartment's rent.
Joey struggles with employment but his stint as Drake Ramoray will have been well paid. Actors live a life of uncertain income, but high income when they have a job. I also seem to remember Joey getting part-time jobs if he couldn't find a part to play for a long time.
It doesn't seem out of character for Chandler to help Joey out if he couldn't make rent.
This answer gives an elaborate breakdown as to how much Joey owes Chandler, which confirms that Chandler is likely paying most of the bills when Joey can't cover his part.