My question is … can a family with 1 kid rent a 1 bedroom property or it has to be 2 bedroom?
You can rent a one bed.
You can rent whatever you like or can afford but given your situation, I would go for a 2 bed if possible - you might want some privacy or head space occassionally.
Usualky yes, but it does depend on the age of the kid and the size/configuration of the non-bedroom space.