I had S1 type issued last September 2015

Do I need to get the basic requirements again even if I have my previous visa?My son it will be his first time, he is 1 and 10 months old this month we will have our flight this August 15 ,and we will apply S1or S2 type any of the two depending on the officer, my husband will shoulder our expenses,he is an ESL teacher there, how much is the estimated amount in his bank account so that our visa will be approved? Thank you for your help!!😊😊😊