and as far as santro and alto are concerned both are 1000 CC cars what i reckon is that you are going to use your car within city mostly and cuore being a 850 CC gives a better milage.
If you want to get a cuore in 500 ks your can get a decent 06 - 07 model and life is just chill. Believe me you wont regret your decision.
Problem occurs when we go for a high maintenance and high cost vehicle. I saw a customer at mechanic today he had an Toyota SE Saloon 04 - 05 model and guess what he was hassling over the price of front wheel bearing and in the end he went for chna made bearing. What is use of keeping a vehicle if you cannot maintain it in a decent way.
If i were to buy a second hand car i would buy some thing that i can keep maintain and drive also. As far as i kept cuore i never waited in the line of CNGs when it was easily available i got it otherwise i drove it on petrol.