@legacy:
I think you are overcomplicating things for the OP (Parth):
he does not want to spend too much on his RPi, so lets him start with the plain vanilla configuration and, only AFTER he grabs how things work on RPi, THEN he can change the typical configuration as you state.
You are only making him confused:
he does not need "performances will be increased by different orders of magnitudes": as he clearly stated he wants:
- "I want to save money"
- "I want to use raspberry pi board for internet of things"
- "I want to learn about programming a pi by interfacing sensor"
- "I am totally new for pi and Python"
- "I want to write and test python program on pi"
For such requests he does not need any superperformance computer at all, just a plain RaspberryPi...
It is clear you (legacy) are only making confusion to a person who is just starting!
He is not a "pro" and I do not think he needs such "high level" suggestions EXCEPT if you give him a really complete and detailed list of ALL of the steps required to follow your otherwise insightful suggestions.
But please remember: he is just a newbie (no offense intended!). You can't overwhelm him!
P.S.: he wrote "I have searched on internet and I found two software putty and xming": surely on those link he have searched for there are some explanations on how to use putty (BTW it is a good app!): you can't throw the stone and hide your hand... Sometime it is better to follow to the letter (especially the first times) the instructions reported on the official blogs/site of the RaspberryPi than to adventure on unchartered waters.
P.P.S.: sorry, English is not my first language and I hope to have not offended anyone!