You should not worry about your criminal background check when applying for a job, if you have never done anything wrong. When you apply for a job, particularly one that works with others, like health care or with children, you should be prepared for this. Though these are not always necessary, there are more and more places that are requiring that you have them.
If you have never been convicted of a crime, you really have nothing to worry about. You may have to pay for your own criminal background check, but that is something that is different everywhere. Some places will pay that for you, while others will insist you pay. Which ever the case, you will not be hired until the criminal background check is completed and comes back clean. Some things might not stop you from getting work, but if you are a convicted child molester, you are not going to find work at an elementary school. That should be the last place you apply for work anyway.
If you are honest about what is in your past, you have a chance at being hired. It will depend on the circumstances. If everyone who has ever committed a crime was denied employment, there would be a far greater number of unemployed people in the world today. There are places that will give you a second chance if you seem to be worth that chance. Always be honest about your criminal background check and you will find a job. It might take you a little longer, but there is something out there for you if you just keep trying.
If there is something that might come up on your criminal background check, but you do not think it will exclude you from employment, you should still say something. There is usually an area on any application that asks if you have ever been convicted of a crime, and there is never a good time to lie about that. You should always be honest. If you say no when in fact you do have something in your past, it will come up on your criminal background check, and that will guarantee that you don’t get the job.