Well i've only ever bought cars outright in cash, and my usual thought process goes:
have i got enough saved +sale of my current car to afford the new one?
Is the insurance reasonable (which for me means less than £800 currently)
Can it get reasonable mileage (cut off here is no less than 25mpg on a motorway run)
am i expecting big bills/is the car expected to be reliable?
If the answer to all these is yes then i'll probably consider it.
Also if it helps, i normally put aside £100 a month in savings, which covers insurance, roadtax, tyres and servicing. That way when they come around annually, i've already got the money saved for it.