If you are hired by a department prior to attending the police academy then you are generally considered a "sponsored" cadet. Sponsored cadets usually have their tuition, uniform expenses, and equipment expenses paid for by the department who hired them. They also get a salary while they attend the police academy, although it is typically at a reduced rate while in training.
Another option is to pay out of pocket and put yourself through the academy prior to applying for a job. This will obviously cost more and you will not receive a salary while you attend, but the benefit is that you will be a much more desirable candidate once you have completed the academy.
Most candidates find it much easier to get hired on by a police or sheriff's department once they already have a certificate in their hand certifying that they have already paid for and completed a reputable police academy. This option will make you a much more desirable candidate.