Some babies will fall asleep on their own at any age even from as early as day one.
But some babies may not fall asleep on their own and need comforting to help them get to sleep until they're 4 to 6 months of age.
By 6 months of age the baby will usually be able to fall asleep on it's own and may cry a lot but eventually they'll fall asleep on their own when they're tired enough.
Newborns will cry a lot until 6 months of age so be prepared for less sleep during those 6 months but it will pass and the baby will eventually learn how to fall asleep on their own without assistance.
Experts agree that it's perfectly okay letting a baby or toddler cry as they go to sleep and will not have any long term damaging effects.
The baby and toddler years go by so fast and before you know it the crying will be gone and the baby or toddler will turn into a little kid and big kid and then adult and you'll actually probably miss all that crying even though you might not think so right now.