You can use LiPo with a T-bar, but it must be a saddle pack. However, no more than a handful of drivers are running that, so set-up information is hard to come by. You will be much better off using a 'link' car and the more common 3.7v LiPo 'brick', as that's what the majority of people run.
In 12th, as in life, if it's cheap then there's a reason for that! RC12R5 / 5.1 or BMI DB12RR second hand are the cars to be seen with for drivers new to the class. Those aren't usually sold cheap!!
Breakages are directly related to horsepower and driving ability. If you haven't run 12th before and you go for anything more powerful than a 13.5, you will break things much more. 12th consumables are tyres and bodyshells - and the more powerful the motor the faster you use them! The better you drive, the less you break things. Again, by choosing a popular car, you will find it easy to get spares, and many people will be at the track and loan you the spare you need. 12th, with 13.5, is probably cheaper than any TC class, and equal to 2WD Off-Road.
There's a free 12th Workshop and Practice Day on 22nd May organised by British Champion and all-round good egg, Nigel Hale - details
here. If you are local to that, contact Nigel. Even if you haven't got a car, and would like to see what 12th is all about and have questions answered, it would be worth asking Nigel for a place. We intend to help with everything 12th - building, tuning, set-ups, driving, etc.
Hope you decide to take the plunge, and that we might see you at the Workshop and Practice Day. If not, find us at the first AMC Shootout meeting at Chesterfield on the 23rd May. Your best bet is to get a car, bring it to the Workshop to be set-up and get some driving tips, and then enter the Shootout the next day to put it all into practice.

HTH