Thinking to buy one, but no idea, which one is cheaper and BEST?  Any suggestion?
Thanks

Nikon d7000

Nikon 3100 for a beginner.

 cheaper and best don't go together my friend. you'll have to pick either a cheap one or the best one. but if you're buying your first DSLR, I'd suggest d3100, d5000, or d5100, maybe even d90 if you prefer Nikon. On the Canon side any of  T3, T1i, T2i, or T3i would do fine. If you ask me which one would I choose if I had to. I'd say d5100 for Nikon, and T2i in case of Canon.
Buying used locally can save money. 

 best, d4. but it costs 5000$. so first set aside your budget. remember, best camera with so-so lens will give so-so pic, but so-so camera with good glass will give u best pic

badarkta dude,
see vids in youtube about the camera that jantare1 mentioned. you will find ur way out.
cheers.

Jantare1 @ thank you for your detail discription, daum@ ke biginner ke end yauta kine pachi aarko kinne bhaneko ke ho that's why middle tira ko bichar garnu parla. sukuchha@ my budget is also around 500 so lets see which one is good for that price. madtech@d7000, its kinda expensive for me. Thank you all for your kind suggestion.