I have flown a few now... DJI Phantoms (4 rotor) all the way up to the DJI S1000 (A sweet machine)
Have only done some dusk flights as of yet. But incorporating NV/Thermal into is simple going to be a matter of budget.
For personal use, there is no certification. You're requred to stay under 400' (some areas even less), and you have to obey rules regarding airspace restrictions near Federal, State, and otherwise restricted airspace. However, if you're looking to do ANYTHING Commercial, technically, you're grounded unless you're one of about 20-30 lat I heard that actually has FAA Permits.
As far as practice... The software that most drones come with is amazingly good at keeping the unit stable. Any quality drone will come with an onboard CPU that interfaces with sensors (usually at least a gyro) that keeps flight relatively stable. HOWEVER, in almost every software, there are ways to disable all of the 'assists' and when you do that all bets are off.
Most of the better drones ($2000 & up) will come with multiple sensors (Gyro and/or IR) that prevent collisions, etc. But you know the story about making things idiot proof. More often than not, you're going to run into problems with batteries/flight times that will cause crashes. And then of course, there's always the unknown/unseen (Power lines, stray birds, or even aggressive/protective birds, rapidly changing weather, and my personal favorite: assholes that might have a right to shoot your drone down if you're over their property).
As of yet... SkyPup is tethered to his Honda... LOL!