I was thinking of that, I'm wondering if having 2 or even 3 of them would be too much for a set? Not too sure yet. I have to do some research into how I want everything to be set up!
You may have trouble using 2 Yetis as most computers will not allow you to use 2 USB-based microphones at once. Yes, you can do a workaround-if you have a mac-using the system audio settings and creating a hybrid device, but it's a bit complicated. For PCs, as far as I know, there doesn't exist any software to allow this same workaround because of the way that the device's data is sent thru the USB bus.
To answer your original question though, you have two options, really. Many will suggest you get yourself an audio interface. I have the Focusrite Scarlett 2i2 - it's a fantastic audio interface for beginners.
As far as the audio interface is concerned, it provides the phantom power you'll need to power up a condenser microphone to use for your podcast. The good thing about having an audio interface is that you can expand it as much as you want, and use it alongside your existing USB mic. It has built-in preamps, and the ability for real-time monitoring as well. Keep in mind, the scarlett is considered to be a pretty good product, I'd say at an 8.5/10 in terms of quality level but it's considered a bit costly by some people. Personally I don't think so, because audio equipment can be super expensive, however you can get a really nice result from the scarlett and a decent quality mic -- results that'll only get better with more expensive, better microphones that you can upgrade with later.
Your other option? Using a portable digital audio recorder. I have the Zoom H4n Pro. The good thing about this is that you can plug in external XLR microphones and not have to worry about owning/operating a mixer or audio interface or even having a computer at all. Also, I enjoy using it for the fact that it's hardware based entirely and it boosts the audio on all of my videos, so I bring it with me when shooting stuff for my channel. It also has built in really high quality microphones, which is a plus. So for $200, around the cost of the Scarlett, you get this plus the microphones it comes with...you can plug in an additional microphone as well to it (I would go with the tried-and-true Audio Technica AT2020, the MXL 990 or the Shure SM7B/Shure SS55 or Shure MV51 you can't go wrong with any of those).
I'm getting tired of typing but if you want to know more let me know.
EDIT: Removed link URLs
