The camera technology changes all the time, so do not buy too expensive cameras if you don’t know exactly what you are paying for. If you will buy second hand, don’t buy more than 3 year old camera bodies.
Interchangeable lens vs lens fixed on the body?
Definitely interchangeable. Forget about the “super-zooms”.
DSLR or Mirrorless:
Having a mirror in the camera body adds to the size, but enables you to see through the lens, helps to focus faster and prolongs battery life as you won’t use the back-screen so often. For beginners, we recommend DSLR’s. Only if size is a very big issue for you, then you can choose one of Sony’s E-Mount (not A-Mount) mirrorless offers (eg Sony A6000) or one of Fujifilm’s excellent cameras.
Sensor size – cropped or full frame:
This relates to the size of the sensor of your cameras, and is in fact the most important choice that can have a significant impact on the quality of your photos. We recommend a cropped sensor camera (Nikon: DX, Canon: APS-C) for beginners.
Nikon vs Canon vs Sony vs Fujifilm
Another hot debate – the answer is that it doesn’t matter too much. They are all excellent companies.
If you want a DSLR, our recommendation for beginners is Nikon, because they have a slight edge vs Canon on the entry segment. Canon has innovated better lately for the professional segment – so they would be our recommendation for seasoned photographers. For the mirrorless, Sony has the best mirrorless offerings around – check the A6000 for the entry segment and of course the Alpha series for full frame. Fujifilm is an excellent option too, if you feel comfortable with Aperture and Shutter speed adjustments.