We have done a lot of this thing over the years. We are a DJI dealer, but have built Cinestars, owned an Alta + Movi, tried frames from DroidWorks, etc. Here is a frame we used to test an A3 flight control with a Light Bridge 2 system and some DJI motor / ESC combos for their line of propulsion systems. It was super easy to build and get ready to fly when compared to everything else we have built. It will carry a small 2 axis brushless gimbal and a 5D Mark III or 6D, etc. The LB2 gives us dual HD video down links, the A3 is a fantastic flight control system and the propulsion system gave us 26 minutes of flight time on 2 x 6000mAh batteries. This was just a proof of concept for a hex frame we are finishing up the design for. On a hex (up to 18 pounds) it would fly a DSLR for 15 minutes.
So if you are looking for a reasonably priced way to get a decent DSLR in the air we can definitely point you in the right direction and get you all the DJI parts you would need. There are also many other ways to do this and most members probably would not want me to crowd up this thread with rambling comparisons of all the different flight controllers, radios, motors, ESCs, props, etc.
Personally I have encouraged people to consider many of the "off the shelf" packages - especially if you are not a DIY type of person. That being said, we have had clients locally build things so big (co-axial hex - 12 motors) that you could not even fit it in the back of an F150 truck. It hung over the sides.
PM me if you want any more information on anything or if I can help you in any way.