We have sold over 30 thousand Wet Suits where those that own a drone can work in the Rain.
Based on this information alone I can tell you that most of those were clients who already worked in the field that they were using the drone in.
So if your working on a tower, than you would have already purchased a drone. If you were working at a Bomb Site and need Bomb Insurance than you would be the one purchasing the drone to use on site. The same goes for Construciton ect.
This is why it difficult to start a done businenss as many have alrady hired or trained Drone Opeators within .
There are a few niches of course that I have seen but few as mentioned
If anything there is a small window as Gadgetguy noted above but if you find your Niche than you can make a go of it but find it first.
Phantomrain.org
Gear to fly in the Rain. Land on the Water, Caputre the Storm.