That is very serious and it will depend upon your friends criminal history in total and the facts of the case. It could be probation to committed time. Make sure he has a good local attorney.
I agree with Mr. Lewis' answer. The typical plea is often an "A" Misdemeanor with a split sentence of 30 days in jail and 3 years probation, but that varies greatly from county to county and depends upon the circumstances and the various ages of the participants. There is no set plea offer or sentence in these cases, but he will be charged with an "E" Felony initially and that often pleads downward to an "A" Misdemeanor with a sentence that is consistent with such a crime.
Rape in the third degree in violation of Penal Law 130.25 is a class E felony. Rape in the second degree in violation of Penal Law 130.30 is a class D violent felony. Rape in the first degree in violation of VTL 130.35 is a class B violent felony. A class E felony for first time felony offender carries a prison sentence up to 4 years but jail time is not mandatory. A class D violent for first time felony offender carries a determinate prison sentence of up to 7 years with up to 3 years post release supervision but probation is possible. A class B violent for first time felony offender carries a maximum determinate prison sentence of up to 25 years with up to 5 years post release supervision but probation is possible. If convicted, he will also have register as a sex offender. I strongly urge your friend to exercise his right to remain silent and his right to an attorney.