questions about the xbox 360 arcade

ok so my dad ordered an xbox 360 arcade for me and i have a question. i know it doesnt come with a hardrive. i know it comes with 256mb of memory. my question is, roughly how much space is it, like how many games.

also just to let you know im not getting live or downloading anything. im not really a hardcore gamer. i get like maybe one or two games like every 4-6 months. so im not going to have alot of games to begin with. im planning on getting Fable 2, Need for Speed Undercover, and Halo 3 soon. then ill just get what i can. so for someone like me, roughly how long do you think it would take for me to need a hardrive for it? and roughly how many games can it save without a hardrive?

I have like 30 game on my xbox 360 arcade , and still have a 155 mb free space .

so don't worry ...

P.S : halo 3 need at least 10 mb