Insurance depends on how big your car engine is, how old you are and how many years' no claims bonus you have, so it's a little hard to say what you should pay without further details. You need to factor in Road Tax, MOT, Breakdown Service, petrol, oil, annual service plus possibly a six month oil change depending on age of car, and an emergency fund to replace parts (eg, I've just had to replace my exhaust). Also if you will be driving in central London, there's the dreaded Congestion Charge. Don't buy a car approaching 80,000 miles, that's when everything starts to go. Either buy well before or well after when major things would already have been replaced.