I got into law enforcement when I turned 20. I had to stop going to parties when I was like 18 though since all that stuff comes up from the background investigation so like Dad said, DUI and drugs are what will get you DQd. Any kind of Dometic Violence will get you DQd more than anything. Also bad credit or history of will hurt you. If you have any shady friends might wanna leave them out of your references lol And for the Oral Boards DO NOT act like a hero. The people administering the boards dont want some cocky a hole and don't care to even ask you to explain why you would grab the M4 and somehow shoot the bad guy 1000 yards away. All these are speaking from experience, not personal but friends who have applied and administer oral boards.
As far as the work, if you like Domestic Violence calls oh yeah your in the right place. I went on a ride along and like 5 of the really senior guys turned off their gps when they went out to the field so others couldn't see their ummmm hiding spots. The retirement is better than mine and I am federal. I don't really know much else except being in law enforcement is like any other job. Its different kind of work but all the BS that I had among co workers when I worked at Papa Johns in highschool is also in law enforcement. They are still people so you can't expect much more or less. Its kinda like if your daughter was dating a paramedic or fireman. Yeah he may save lives but your ignorant if you think that he isn't sticking his fire hose or thermometer in every hole of your... well you get the point.
If you're really interested in Law Enforcement you should check out federal areas as well. Try
USAJOBS - The Federal Government's Official Jobs Site they have tons of listings! Also don't limit to just LAPD, CHP is always hiring which pays more and has better retirment.