Hey Thomas, I've been working freelance for roughly six months now after working as a videographer at a local news station for years. I've always worked with bigger companies doing freelance work, making marketing videos and social media promotional videos and I personally normally 75-100 U.S. dollars per 30 seconds, and 5 dollars per edited photo (minimum 20 photos).
It is always good to have some sort of contract, that way you can guarantee your payment. I would also always be extremely open to whatever you client wants, more often than not people will tell you to "do whatever you want, just make it look good" but then they'll want something changed after you have finished your edits. Even if you think what you have already edited looks better, it is always best to keep your clients as happy as possible, but don't be afraid to respectfully disagree if they suggest something absurd... after-all you are the one with the film degree.
Another very important thing to do in my book is always try to give more to your client than you originally promised. Whether you are giving your client a few extra pictures, or a 15 extra seconds of video... it can go a long way with clients and you'll be able to keep them as clients.
Hope this helps!