TiVo HD and Cox question

I recently found a TiVo HD for $5 at my local thrift store. I'm currently using it with an OTA antenna. I also have Internet with Cox and I'm looking to use a cable card with the TiVo. I saw that the card is $2.99 a month to rent. Could I rent just the cable card and get channels, or do I need to pay for a package? Also, could I access On Demand programming (i.e. SyFy and FXX if I'm subscribed to these channels)?

Oh, and what would everyone's ideal setup be with this current configuration? Unfortunately, I cannot activate the TiVo service to record, but I could still pause and rewind.