had the plans from when we built the house that showed the “future basement”. Typically as long as your not changing any load bearing walls or anything like that it doesn’t take much to get the permit. My city has a check list I was able to follow that and just called out anytime I needed an inspection. I think I only had 3-4 inspections (4 way, insulation, drywall, and final inspection). I passed most of the inspections first time except for once and he just came back the next day after it was fixed.