Canon C300 MK II. I haven't owned the camera and I haven't used it or tried it out. I would buy a C300 MK II not because of it being an expensive camera, but because of the look it has on clients, the High dynamic range when you are in a dimly lit scenario and you can't change the lights or bring in lights (big reason), cropping/zooming in in Adobe Premiere for HD playback for some clients when you mess up a shot, saving an overly exposed shot or under exposed shot in post, auto focus feature to save time when focusing; EF lens mount, because you may want to use a spare photography or vintage lens, and those are cheaper. Built-in ND filtration is underrated, because ND filtration I can see being useful in plenty of situations where there is too much exposure.

Don't buy anything that you can't go higher than 6400 ISO with, because clients are picky about lights, and you don't want to lose your production job to someone who shows up with a JVC camcorder because you couldn't talk your way out of a situation.

Lenses, and this time, because you are working documentary, get a sigma art 18-35 and sigma art 50-100 and also a 24-70. Get a 70-200 lens too, and maybe even a 100-300. Be sure to get some low light primes, because you need the shallow depth of field when you don't want to get sued for unnecessary people's faces being shown; their faces should be a blur.

You may also want to get a zoom lens that goes from 45mm-300mm for a long zoom.

Get a good laptop or desktop to handle all of the high bitrate footage. I doubt people truly know that some Dell $200 laptop can not handle 4k footage.

Don't get cameras made too much for cinema either, because an 8k Red Weapon would be a nightmare to handle for a run and gun documentary person on a budget. You are on a schedule, you don't have time to color correct, and you don't have time to color grade quickly. Blackmagic Ursas look like a nightmare too.

People don't care what goes out of your mouth, but instead what you film.