accessible somehow, are somewhat risky to gain access to in person
If you are going to be flying in places that are "accessible but, are somewhat risky to gain access to in person", then you need to practice flying more "at risk" than scaring the daisies in your wife's garden.
You have got to get "sweaty", fly it in your house or business, down hallways, FPV only… Fly into closets, turn around, fly out… Fly under a desk, fly out, again all FPV, Fly into and out of your car or truck (FPV)… remember, your drone cannot look up so flying vertical (as in going from the first to the third floor…) FPV is more luck than skill…
When you do any of this, you do it really, really slowly, a few feet at a time, stop, Yaw 360 degrees, slowly, looking for obstacles, raise and lower your camera.
Flying inside a structure, means that you probably will be flying Atti Mode with no GPS. That means if you are flying in a breeze, that breeze will carry the drone along with it… Also, flying in confined spaces means that walls "suck" drones into them if you get too close. It all has to do with the Aerodynamics of thermodynamics (the difference of sucking and blowing…")
Remember when our troops went into Osama bin Laden's compound, the helicopter that landed inside that confined space with walls all around, could not take off again. The Seals, along with the flight crew and everything else, (the body…) we took from the compound had to be evacuated in separate helicopters that landed outside the compound and we had to blow up the helicopter since it could not be recovered…
One final thought, when you inspect portions of a build that may not have seen the light of day for a long time, that area will be dirty and dusty. You Drone has a lot of Prop Wash, don't believe me, lift off and hover 6-12 inches higher than your head and then stand under it. Try flying it a few feet over a pile of sawdust…
And you will probably want to buy a light to illuminate the path, you might not think it's too dark to crawl around in that confined space, but your camera may not pick up enough light to fly FPV…
Good Luck and leave those flowers for your wife to pick…