No less than a Canon 1D-X level body which will run you about 4,500 USD and you'll have to shell out about 2,000 USD minimum for a lens that has a low enough aperture setting and exposure time quality
All in all you're looking at about 7k new, which truth be told is cheap as fuck when it comes to Cameras.
Used you could probably get away with shelling out around 4,300
If you work at it you could make enough money with sed purchased equipment to recuperate all the money you spent on them in the first place. That's the beauty of photography