Ensure that you fully research your state's requirements. Every state has peace-officer standards, as well as a training council (P.O.S.T.) or commission. Fully research the state's requirements for certification. Most departments use this as a baseline, and can require more if they desire and explain why. Check out the medical requirements (such as vision and hearing), physical standards (such as physical training improvements), educational requirements (such as GED or college), and psychological requirements — you may have to be tested. Speaking a second language can give you an edge.
When it comes to background checks, each state has its own requirements. Some may allow life's youthful misadventures (such as a juvenile record). Others may take strong stances on recent recreational drug use. Some states are lenient, while others have no sense of humor.
Even if you feel you will make all the grades, this investment will not ensure you employment. Granted some departments seek certified officers but this is not a sure win. Our men and women of the Armed Services are granted Veterans Preference Points for their service to our county. Whether you agree or not, military veterans (like me, Hooah!) get them and may well score higher. This is life.
If an agency you desire to work for is under any consent decrees for past hiring sins, and you're not the ethnicity or gender they're seeking, you may be out in the cold. There is no guarantee in life, except death and taxes.
For you to invest your time, effort and a pile of money to become certified is indeed laudable. Before you do this, you must thoroughly investigate your prospects and weigh your chances. If you feel up to the challenge, go for it. I wish you the best. I don't want you to waste your time, effort and money if this is a pipe dream. If you're going to try this, give it all you have.