sounds like this scag hasnt been taken care of, who in the world leaves a mower lay around without cleaning the deck for a year? i wouldnt trust it, id look the other way my friend! and the min deck size your going to want is 52", we use 61" . your going to want a rider as well. something you can add attachments to in the future!
id just hold off untill your 16 and can transport everything, then you'll have a nice bit of money saved up to buy everything outright.