Chandler did well in his job as a data analyst, but not well enough. According to Glassdoor, the average salary for a data analyst in New York City in 2021 is $84,892. Which is not bad at all. But Chandler lived beyond his means. We'll adjust his salary using an inflation calculator to 1997 dollars, because that was the year a "Friends" fan used as the baseline in a detailed calculation of how much money Joey owed Chandler, per BuzzFeed. In 1997, Chandler would have made $50,614, using a simple 1:1 dollar comparison.
According to BuzzFeed, Chandler and Joey's rent was $3500, and for at least three years, Chandler paid it all. That's $42,000 a year. On a salary of about $50,000 (before taxes, mind), that's impossible to afford. Many landlords require that tenants make 40x the monthly rent, as explained by StreetEasy. To afford that requirement at $3500, Chandler would have had to make $140,000 a year.
HUD categorizes renters as having a "severe rent burden" if more than 50% of their income goes to rent payments. Chandler would have been paying somewhere around 84%. And after he switched careers and became a junior copywriter, forget it. According to Glassdoor, a junior copywriter in 2021 makes about $56,000. In 1997, that would have been about $33,000.
In real life, Chandler wouldn't even be able to support himself the way he lived on the show, let alone support Joey, too. The only way he could have afforded his lifestyle is if his rich mom, Nora Bing, was paying for a lot of it — or at least serving as his guarantor. Which would actually make him a very realistic depiction of a young person in New York City.