tv show and movies on iTunes?

Is there any way of knowing how BIG a TV show is before purchasing it? I would like to know this due to limited space on my iPod (about 1.5GB left) and also internet usage reasons. If there is no way of knowing this before starting the actual download, could someone please tell me approximately how big (in MB or GB) a 20 minute TV single episode will use up (in internet data and also on my ipod).

And with Movie renting, which is usually a fifth of the price as a whole DVD, how long do you rent it for and how does this work?

Thanks,

courtapple 🙂