PSP save games...?

I'm thinking of buying a PSP soon and I'm wondering, does the PSP save to an internal hard drive (Like the PS3) or do you need memory cards (Like the PS2)?

Also, if it does need memory cards then whats the best one to get?

The PSP Go has 16GB of internal storage. The PSP 3000 has 64MB. The biggest memory stick you can get for the Go right now is 16GB and for the 3000 is 32GB.

And the PSP memory cards are bloody expensive :evil:

this is the best choice IMO

http://www.amazon.com/Sony-Memory-Stick-Flash-MSMT8G/dp/B0013AZ19G/ref=sr_1_1?ie=UTF8&s=electronics&qid=1266033639&sr=8-1

OK, well I know I'm definitely not buying a Go and that I'm gonna be getting the 3000 instead. But I have one more little question. How much space does the average PSP save game file take up?

Thanks for all the help. :)