If i buy an at&t iphone 5 can i start using it prepaid?

I know that at&t has a $25 a month prepaid card. Would that still work if I buy an iphone and use it as a gophone?

No. ATT does NOT allow the Iphone 5 to be prepaid… You will need to get the ATT Iphone 5, jailbreak it, unlock it via app in cydia, and use Tmobile prepaid

You can use any phone on prepaid… However, the data will be most cost effective. Postpaid is the way to stay unless you use another prepaid carrier like T-mobile, Simple Mobile, H2O etc…