It has been confirmed that we get 20,000 credits to start. Not sure on cars though.
Well there is not nearly anything for the money at the dealerships, and the used car dealer will have like 3-4 in stock that you have enough money for. 1 being a MX5 and one Gallant, that's about as much as I remember. But after doing license 1-2 (eg. C B) you get 2 nice cars that help a lot tackling amateur series.
Also can someone with the game answer this question about the prize ticket system:
Do you actually get a ticket for a unique car that can't be obtained anywhere else or just a random ticket or what?
You get a Ticket when you win a series. That ticket can be used by entering the "Car Delivery" from the main menu. Then you see all the ticket you got at the moment, if you pick up you get that car added to your garage and the ticket is gone. Just a 2 stop pick up to new cars instead of putting em directly into your garage. I guess it's there just to make you happy 2 times. First when you win. Second when you are back in the menu.
And somebody questioned the GT5P connection. Well there seems to be none at all. I did not do an extensive search, but did not find any point in options considering GT5P. I have a full save of GT5P on the same PS3, yet nothing showed/poped up.
Can't answer the PSP related questions. I don't have a PSP