I have a Canon DSLR which cost me £400 but to be honest my Samsung s7 takes decent pictures.
It's about planning the pictures rather than just snapping away...position the car against a background or backdrop that makes it look attractive, make sure it is clean (especially glass) and tyres nicely dressed (I go for a Matt look rather than tyre paint!), start at the front then walk around getting all the flattering angles - low down always looks better than up high looking down.
Just take your time and realise you want to make the product look as attractive as possible to the buyers. Avoid filters though, I found out to my cost several times that whilst 'pretty', they give buyers the idea that the car is flawless or maybe a different shade of blue than what's in the picture etc...you get the idea.
I'm now into the idea of video walk arounds as per several other members, you get the chance to point out everything (flaws included) in a sympathetic way and I can see how it builds trust with buyers.
Cheers and good luck.