Tri-Caster with composite inputs seem to be pretty cheap. I have been wanting a Tri-caster for a long while.
I have been looking at the Videonics switcher that can be added to by the control port in the back. Title maker and maybe a few other items I can not remember.
Maybe a mixer.
USB camera and a video editor seems to be very basic in video these days.
Screen capture software is another good one to have.
I bought a camera at the local pawn shop that is SD with hard drive for $50.00 US, I think.
It had a table top tripod, box for another camera and cd for another camera. I bought a S-video cable with sound and composite rca connections. It had a power supply and battery but not base for USB out put.
Live feed, I have seen software for sale. edit:
Prices seemed to be high. This was years ago.