On the mini front, just remember they are really bad cars. they're just good fun when they work. i've had mine over 20 years and dunped it twice! i'm just bringing it back to life for the third time at the mo. I wouldn't use a mini as a main driver either if you need to depend on it as it will probably let you down. ( that should get me slated!!)
As for the credit card, i bought my last car on an interest free card over 18 months. just make sure you can make the payments or you will get stung..
Good luck
best thing to do is research research and research before you even go and look at any mini's. find out what to look for and how much it will cost you to repair etc.
paid 1300 for my most recent 998cc F Reg flame red mini and it does 175 miles a week minimum with my work alone and recently did a nice 187 mile journey down to weymouth and back in one weekend with no problems, guaranteed they can and will break down but as long as you keep your eye on it and service it every 6 months i dont see why it cant be used as a daily car.
all the best either way!