Talk to an attorney before you turn yourself in, and definitely before you make any kind of statement to police. It is very common that these types of charges can be reduced, or dismissed entirely, with a good lawyer. Talk to someone who practices in your area today if you can. And definitely don't say anything about the facts of the case on a public website!
You really need an attorney to talk with you about your specific situation. If you can't afford one, you should try to borrow some money to pay an attorney. The courts will appoint a "public defender" if you can't afford a lawyer. It seems to me as though prosecutors often charge a bit worse crime than they can really prove in order to allow some room to plea bargain down to what it actually should be.
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You need to call an attorney immediately. Do not, NOT speak to the police about this incident. Seriously, say NOTHING. The cops will twist what you say and your words will absolutely be used against you. An experienced criminal defense attorney will be able to act as a go between so that you never deal with the police outside of booking.
Although, these charges are almost always reduced, it's tough making a prediction about jail without knowing the circumstances of your case. Particularly vulnerable victims (old, infirm, etc.) can make things more difficult to negotiate. The amount taken can also be an important element. Lots of money means a more difficult prosecutor.
Feel free to call my office to discuss the facts of your case so that I can give you a better answer. Of course, the call is free.