Go to Walmart site and enter something like "Win7 laptops"
When the results appear, further filter them to show Dell and Lenovo.
There you go, look for at least a Core2Duo that runs at 2.2 (at least 2.0)GHz and has a minimum of 4GB RAM. You can even get some on ebay without an OS or even an hard drive (add a SSD).
Don't need to spend more than $150 give or take 50, especially if comfortable adding more RAM or a SSD, if desired (it is desired).
A newbie is better off with a non-UEFI Windows 7 computer, to begin with, IMHO Have fun and . . .
Thank you very much @sp331yi really appreciate your advice. Just being little greedy, could you also give me advice on which distro to start from ? I am more interested in hacking side and I know I have to work very hard to learn it. Currently, I am working as a network technician and also learning python at the same time. Thank You again.