You don’t need a helicopter or fancy plane. An ordinary Cessna single engine, high wing plane is probably the most effective. My mom learned on a Piper Cub J-3; these are so slow and have doors that open so these are even better. Of course Piper Cubs are antiques today so you won’t find them everywhere; they were just the cheap alternative back in the old days.
You want windows that open. Slower planes are more likely to have this than your dad’s corporate Gulfstream.
I’ve never felt the need to pull off a door. I’m just fine shooting out an open window, and this way you don’t get blown all over traveling to and from your target.
I’ve also never cut a hole in the bottom of a perfectly good airplane. Shooting straight down is done for mapping and surveying, but makes boring photos. You can pull these sorts of shots off the internet if you just want to look in your neighbor’s back yard. I prefer shots made at a more natural angle, which you get from shooting out a window.