Even more to the point, your scores should be great for a mortgage in several years. Your EQ score and overall financial picture are crazy good for someone your age!
Just keep working what you've got, including the lower limit cards, as long as there are no fees. Think about something you could do with those two twice a year, and write it on a calendar (gas for your trip to the beach in the summer, Christmas shopping in winter.) Let each report at the magic 1-9% (not 0%, not 10%), and then park it again. As you are so young, you should really hang on to all four cards, especially since the $700 card is your oldest, and still less than a year old. If you do nothing else, never be late with a payment.
If you have bought your FICO EQ and/or TU scores, play with the simulator and see what it favors. The numbers aren't guarantees, but they're a guide. Don't just do the best scenario, play with the others down below. "Pay down your credit cards over 24 months" appears to mean be smart and behave yourself for the next 2 years. I wouldn't torture your accounts with slow repays.
I'll leave the best-deal-on-monthly-FICO-pulls for someone else. I'd bought so many that I could support a credit scholarship fund!
* Credit is a wonderful servant, but a terrible master. * Who's the boss --you or your credit?
FICO's: EQ 781 - TU 793 - EX 779 (from PSECU) - Done credit hunting; having fun with credit gardening. - EQ 590 on 5/14/2007