Time doesn't matter much at all, there's never such set time frames when things should happen. Could take him a day or 50 years to get comfortable enough to see somebody else either friendwise or romanticly.. Depends how you know him/how long you known each other or raport level or how you feel around him (Do you feel safe enough?) Pull him aside where its mutual place (Def no bar scenes, that's kinda cheap and sleazy for this and he may not take you serious) and say something like, 'Hey, I know things might be tough for you, and _your input_'
That way he will have lots of respect for you and may not become jaded by women especially if his last relationship ended bad.. But hey, if you try to pursue him and end up with him for the long haul that's great yet if not than you tried, try to wish him luck
Just be friendly, but do not pursue anything more, wait until he shows hints of wanting more from you, then you can start getting flirty and making hints to him you want more, but allow him to make the move, otherwise you could just be a rebound bunk up,x
It really depends on how long his last relationship was, but after a month he won't be ready. A good of thumb is it takes about half of the time of the last relationship to get over it. In other words, if his last relationship was two years, its going to take him a year to be emotionally ready to engage in another relationship.