Now that I think about it, you can basically start off with ANY car. I don't think there should be an all Kei car class to start things off. I think a person can take a Mini Cooper S of today, and boom. You already have the 160 horses, then more hp with an oil change. There should be enough money to purchase more upgrades to assist you in your GT4 endeavors.
If you ask me, I think the game will probably start you off with more money, that is if my "Sim City" example pays off. "Sim City" was one of my favorite simulation games. You build a city from the ground up and take care of it. I played the first one on SNES, then moved up to SC 2000 on my PC, then SC 3000 (my computer doesn't have the proper requirements for SC 4000). All along the way, the reward kind of increased. So as I played Sim City 3000, I had 50,000 simoleons (the currency in SC3000, and "simoleon means money, in one way or another). 50K was enough for me to build a power plant, some streets, homes, offices, factories, police/fire departments, and schools. So if the game starts you off with 20K, it will allow even beginners to get a BIG learning curve. You can start the game with a Mini from either today or the past (sure to make MiniMADness happy) and upgrade it about 20-40 percent to go racing. But everyone will start off different in GT games. I know that my path to glory isn't as detailed as the next person, but we all start someplace, and meet our destiny at game's end. So go out there and race already! Keep up the good work, PD!