I felt in love with the speed of the nitro cars after watching a racing event a few weeks back - and planning to start myself
1. Should i start with battery or nitro? I prefer the sound of the nitro cars of course but i do not know much about engine. And the battery cars seems to run as fast as the nitro but only a short while - how long do the battery cars run anyway?
2. Is it ok to buy 2nd hand car sets as my budget is limited?
3. What noobie model should i look at? I prefer noobie models which can be upgraded over time as i improve and have more $$. By the way i am into the touring car models, no trucks/off road please (maybe i should post in a UK site?)

Thanks in advance for you help.

Welcome to the hobby. Weather you decide to run electric or gas is a matter of preference. Many will tell you to start with electrics but if your preference is gas go for it. In either case you have alot to learn, be it tuning a 2 cycle or providing the proper gearing for a particular electric motor.
The length of time an electric will run depends on a number of factors. The power of the motor, battery strength, and gearing all influence both the speed of the car and length of the run.
As far as cost of getting started into racing I believe it would cost more to go with a RTR electric car. Besides the cost of the car you will need decent batteries, motors, and a good battery charger. These can add up to alot. If you go with a RTR gas car you need only to buy fuel and a glow starter to get on the track.
Buying used is a good way to get into the hobby inexpensively. Just be careful as a badly abused car may cost more to repair than just buying new. Have someone check it out first.
Get to know the people at the local track. They will be more than willing to help you help you get started. They may even have a good deal on a used car. That's how I got started

Since you are a newbie, just go with electric. And if you may race sometimes, or even if you are just bashing around, I think the Team Associated TC3 is a great start. If you just want a cheap car, but still has some performance, the Traxxas 4-tec is a good place to start. BTW, electric cars can last as long as nitro cars, with the new technology in batteries. What second-hand car will you buy...i wouldnt think its a really good idea to do that. If you want more information, just PM me.