I love how helpful we can be.
That aside, if you just want a metric ton of money you can use something called CFW and CWCheat on your PSP. Being as I'm not exactly in what the PSP would call its "target demographic" that stuff is more in depth than I would care to go. I would suggest reading up on it much more than I have before trying it. (I simply know of it and have a general idea that it gives you credits to buy cars.)
As to people who ask why you'd want a shortcut on GT... Some of us really like the game but lack the time to devote to it, or maybe we're more casual about it. I'm somewhere in the middle; I'm way more hardcore about it than a large portion of players but way more relaxed than probably 66% of the people who poke around on GTP. Will I end up cheating? No, probably not mostly due to the fact it complicates playing the game, and takes some fun out of it.
But I'd really like to get the cars sometime soon, and given that I work around 60 hours a week I don't see that being all that doable.