That's kind of what I was assuming. I thought the buffers had something do do with getting around bandwidth issues. I don't know how it translates calculation-wise...the question is still "How much kbps do I need?"
Unfortunately the only good answer based on the information you're able to provide right now would appear to be, "It depends."
If you want to be realistic the better question to ask is what resolution and quality combination is viable within the restrictions imposed by your recording equipment/conditions and the bandwidth you can afford? Under optimal conditions 3Mbps for 1080p podcasts is entirely reasonable. Presumably optimal isn't an option. Until you know just how far off you're looking at you haven't really even formulated a question yet.
It seems like you have a pretty good idea about the content so that's a start. Next you should probably focus on the camera and lighting.
Do you have a camera already? If not do you have any in mind? If not what kind of money are you willing and able to spend?
Do you have an environment available with a good backdrop and lighting conditions? How about just the backdrop and a budget for some simple lighting? One trick I learned while working as a musician many moons ago was the creative application of cheap track lighting. Add in some dimmer switches and DIY lighting gels and you can manage surprisingly good quality for not too much money.
And don't forget to figure audio into your budget. There are a lot of options, depending of course on the physical constraints of the recording environment. This isn't directly relevant to answering your question but if you have a starting budget make sure to figure in something for microphones. Fortunately you can get surprisingly good results for not too much money. The CAD Audio U1 podcasting mike I use cost me $25. Eventually I want better but it's a great starting point.