In-line is like people with MBAs - Maybe Best Avoided. Lots of people are finding those cars tricky to drive, whereas, as Trev says, there is plenty of success being had with the sideways cars. Your best bet is any from the CRC, AE and V Design with a sideways layout, and there are usually many available second hand.
If you buy second hand, please get the car to any of the many people at Nationals who are volunteering to help new drivers, and have one of them rebuild it. Most people get rid of their 12th cars because they can't get them to handle. That usually means they haven't built them properly, so despite them being immaculate/excellent/BNIB or any other likely description, there's every chance they will be built poorly.
Trev will prove the exception to that Rule, so you could do no better than getting in on his immaculately tended collection before they hit a well-known auction site!
HTH
