Characters in their early 20s in entry level jobs live in apartments they could never afford on their salary. Especially common with main characters.
Friends and Big Bang Theory are two that come to mind.
Courtesy of Google, the apartment Sheldon and Leonard share would go for around $2k per month. Penny's would be cheaper as it's one bedroom but unlikley some-one on minimum wage could afford it.
In Big Bang Theory, only Penny has an entry-level position. The rest have been at their jobs for years. In Season 6 an episode stated all of the guys (well, except Howard) were on the short list for tenure.
Re:
The Big Bang Theory:
The characters also live in downtown Pasadena (City Hall is clearly visible from the window adjacent to Sheldon and Leonard's kitchen. As they're all scientists and doctors (sorry,
Miiiiiiister Wolowitz!) at CalTech, they likely bring home respectable salaries. I don't have any trouble believing Sheldon and Leonard would be able to handle a $2,000/month rent with their combined incomes.
Penny's a different story obviously, but she also spends most of the series waiting tables at The Cheesecake Factory and acting on the side, so I'm sure she was able to squirrel away enough money each month to afford her much smaller one-bedroom apartment before she went into pharmaceutical sales this season.
Re:
Friends:
Having re-watched the series since it came to Netflix a few weeks ago, it's important to remember that Ross is also a doctor/PhD at a museum and then later a university and likely earned a generous income.
It's made clear in the first season that Monica and Rachel's gigantic apartment was actually owned by Monica and Ross' deceased grandmother. Chandler and Joey lived across the hall in a much smaller, less impressive space comparatively.
Chandler works his way up the corporate ladder at his job before switching careers to work in advertising. Monica becomes head chef at a restaurant.
Joey finds success as an actor first when Days of Our Lives brings him back to life as well as various major movie roles (the World War II film he does with Gary Oldman, et al) and his own hour-long (if short lived) action TV series ("Mac & Cheese"). The residuals alone from these would be great for his income.
Rachel also works her way up from waitressing at Central Perk to working for Bloomingdales, then Ralph Lauren, to being high value enough for Ralph Lauren and Louis Vuitton to start a bidding war over her employment by the time the series reached its final episodes.
About the only character who doesn't seem to make much progress in her career is Phoebe, who is still a masseuse and musician performing at Central Perk by the end of the series but has also married Mike Hannigan and is largely unconcerned with the progress of her own career anyway.
So, despite the usual trope of young 20somethings living in extravagant residences despite the low income they might be making, I don't really see how that can be applied to these two specific shows.