How much should rent be of income?

I'm curious to know, what is the ideal percentage of one's income that should be allocated towards rent? Is there a general rule of thumb that financial experts recommend? I understand that this may vary depending on individual circumstances, but I'm looking for a starting point to consider when budgeting my finances. Additionally, how does this recommendation change for those who are just starting out in their careers or for those who are more established in their financial situations?