No one will give you odds or chances of how hard it is to get a bid in general, and certainly not for individual fraternities (they are fraternities or chapters, not houses) in particular.
According to these FAQs, first semester freshmen may NOT join. You have to have at least 12 credits and a 2.5. (PS: you should have found this website on your own.)
http://fasa.syr.edu/about/FAQs.html