Let's assume defensive shoot on the street. And Let's assume that you are uninjured. Police show up. Better not have gun in hand when they arrive. You're gonna get proved out and cuffed right away. Your gun and bad guy's weapon will get bagged and tagged as evidence. You're gonna get transported to the station (unless injured. I've seen some advise you ask for medical attention no matter what...claim chest pains. The theory is you can delay sitting in a cell.) You're gonna be stuck in a cell until you get put in an interview room. You may or may not have your lawyer. Police may or may not make statements around you to try and get you to waive counsel and make a statement. Depending on the jurisdiction and politics, you may be charged and booked until your initial appearance in court, where a bond may be set (some jurisdictions are going no bond for shooting offenses at initial appearances). Police may seek a search warrant for your home, seeking any/all weapons and ammo. They may ask for the combination for your gun safe. They present the case to the grand jury, and you end up indicted. Then it's plea bargaining negotiations and trial prep.
Frankly, a lot will depend on how anti-gun your area is. If it's a clean shoot with strong evidence and a gun friendly community, you may not get charged immediately, or your case may get kicked before/at grand jury. You'll need your lawyer's help to get your property/guns back.
Then, the civil suit comes. That's a whole different mess.