Well it can take 3 months to 3 years until he feels comfortable on the ice. My honest opinion is to start him out with roller hockey its a lot cheaper than ice and you can still develop shooting and puck handling skills, but i would also recommend him doing learn to skate/tot hockey/ pre hockey as well.
You should also be aware of the high cost of hockey if you do not already know. $2,000-$8,000 a season depending on the club and level plus all of you equipment and travel expenses. House hockey travels as well too.