Kind of an odd question as the variables are huge. You staying in a hotel, with friends, eating out every meal, doing the tourist thing or living simple? I'd budget $2,000 for food, $1,000 for entertainment (not including booze) and accommodation....nice hotel downtown Montreal would be $120 a night, cheap motel would be $50 a night but you'd need to ask for a monthly rate. Once you add booze in (and there are numerous drinking opportunities in Montreal-it is French after all) you'd better be packing a load of cash if you want to have a really good time. Better reckon on $6,000 as a bare minimum unless you can sponge off friends.