Time Machine Q. please.

That's more then enough for Time Machine. It depends more on how far back you want your backups to span and how much data you're actually going to have.

 

plenty of space! time machine doesn't back up anything thats included on a basic osx install, so that saves you a ton of backup space/time.

 

I think there are some 1 TB HDs on Newegg.com for a little over $200

 

Unless you tell Time Machine to exclude System folders, hidden Unix folders, and anything else you exclude. Time Machine is going to backup everything on the hard drive.