Sumo19 writes ". . . he could go to prison for any time the judge seems fit". That's not strictly true because (unless there are very exceptional circumstances) judges have to sentence in accordance with the guidelines in this document:
http://www.sentencing...inst-the%20person.pdf
See the table on page 13. The sentences there refer to first-time offenders, convicted after a trial. Previous offences (particularly for violence) can push the sentencing range higher. An early guilty plea can see the sentence cut by one third.
So the minimum sentence is likely to be one of 2 years imprisonment (of which 1 year will actually be spent 'inside').
Chris