I use my TV monitor to stream video while I'm working on my computer screen. My computer is about to crap out. Do I need to purchase a dual video card in order to make this work or will just one video input and one HDMI port be enough to run them at the same time? I don't care if they show the same or separate images...I can always work split screen, I just need to be able to SEE them both at the same time.
You do not need dual video cards to have dual monitor hook up. You need a video card that supports 2 video outputs. So make sure, when purchasing a video card, you look for a card that has multiple video outputs, such as an HDMI and DVI or whatever outputs you have on your monitor/tv. Let's take mine for example. On my work computer, which is notably old, it has an NVidia Quadro 600 Video card. It has a Display Port and DVI port on the back of it. So I have 2 monitors hooked up to it and they work just fine, it's just a matter of adjusting the settings to how you like it.
Notice how it has multiple video ports. It should also state, when you are searching, whether it supports multiple video output or not.
You can also choose how things are displayed on your dual monitor set up. Once you have the new computer, you can simply right click on the desktop, select "screen resolution", and it should bring up a screen such as this:
Under the "Multiple Displays" menu you can select to either "Extend desktop to this display" which will allow you to have an extended desktop, but won't mirror what's on the main desktop. Or you can choose to "Duplicate Desktop" which will mirror what's on your main display. I would choose to "Extend desktop".