Is $50,000 a year a good enough salary to live in Singapore?

Median gross monthly income 2019 is $4,563, inclusive of employer cpf contribution. You would be earning slightly about more than 50% of the workers, therefore if you are frugal, definitely enough. That being said, your jobs should also have opportunity for pay raise, else $50,000 in 20-30 years would definitely not be enough.