When i was younger (29 now) and living with mom, these are some of the things i said to convince her:
-some mothers would be grateful that their child was spending
money on apet instead of drugs/cigarrettes
-snakes are clean and quiet
-take much less space than a dog
-don't mess on the carpets
-can deter burglars
-will teach you responsibility and compassion for living things
-cost much less per year to feed than a dog
Or, you could just sneak another in and hide it.....only kidding!!! =)