My DD satrted walking 1 weeks before her first birthday, my sisters DD#1 started alking at 8 months and her DD#2 didnt walk until she was almost 2.
All kids differ, my neice actually had a problem with the bones in her foot where they didnt form properly so its a good idea to get him checked if he's not walking by 18months just to be on the safe side.
Dont get me wrong everything prob fine with your little one some kids just take longer.

Good luck and enjoy it while hes not walk cause when he does start you'll kinda wish he didnt once he starts reaching even more things. lol