Do you have any time in small piston helicopters? If not you will probably need a few hours to get use to the way they fly compared to larger helicopters. Helicopter training has gotten very expensive over the past few years so expect to pay $300+hr for a R22/S300 instrument trainer or $425+ for a R44.

I would probably check into Bristow Academy for the best streamlined program. It may not be the cheapest but with helicopter training there just isn't huge margins of cheap vs. expensive unless your comparing doing the training in different types of aircraft.