Limited range
Most notes sit within a comfortable span rather than jumping to extremes.
An easy song is not just a famous song with simple lyrics. It should sit in your comfortable range, avoid constant strain, and give you enough time to breathe and phrase naturally.
Most notes sit within a comfortable span rather than jumping to extremes.
Patterns repeat enough that you can learn them by ear.
Lines have natural places to breathe without rushing.
The song can be transposed if the original recording is too high or low.
Start by choosing a song that nearly fits, record one phrase, then check whether the hard part is pitch, breath, range or timing. The best beginner songs let you improve one skill without fighting the whole arrangement.