How long have you had this male? How old/large is he? Are you offering the same prey that the prior owner did? When did he last eat for his prior owner?
ETA: While I would never advise someone not to take a critter to the vet if you suspect it is sick, black pastel and cinnamon morphs are known for "squeaking" when excited. I think it's related to the "duck billing" that the super forms exhibit. I have a black pastel het hypo female that has squeaked from the day I got her; two different vets have both said she doesn't have an RI.