i just got a white psp and i wnat ot play homebrew!!!

Umm, look around the forum first, dumbass. Your answer is everywhere.

youl have to fork out for a modchip

Don't give up yet check the general area before buying a MOdchip
posts
2.7 downgrade THEORY

And there may be other development in the future for 2.71 or even in 2.8 an someone may find an exploit in 2.9+ ,so fingers crossed.

Show some sympathy and don't call someone a dumbass.

Yea, I know, but I like callin people dumbass. It's funny.

but then how can i download homebrew and play on 2.71
and i also asked places and they told me that my psp can't be moded

At the moment you cannot run homebrew on 2.71 nor downgrade from 2.71.

OK, I'll correct myself; with the TIFF exploit it is now possible to run hombrew from 2.71:
http://www.psp-spot.com/forums/index.php?showtopic=27430
At the moment it is only a Hello World POC, but the future is looking good for 2.71 homebrew.

so deos that mean i can play homebrew. and i am not sure if my psp are that are going to brick if i try downgrade

It means that you will be able to play homebrew in the near future (next few weeks should be interesting).