The first thing i'd say is dont bother getting one on finance from a garage unless its a decent rate, get a bank loan instead, its likely you'll get a better rate. It depends on what model you are looking to get, how old it will be, what the APR on the loan will be etc.
I wouldnt want to get financed up on an old 172 at 19% for the next 5 years for example, but if there was a tidy cup or 182 about and you get a decent finance deal and can affod it without being skint, then go for it.
They are great cars, but not great enough to be skint for years to come to be honest.