Monthly budget

The obvious answer will always be 'it depends' - based on what kind of lifestyle you want to live but here's what it has been like in my experience- keep in mind I don't claim that this is true for everyone- just for me. And even for me, spending changes drastically depending on if I'm saving that month or dating....

As far as food goes, if you plan on eating local Vietnamese food at the typical street vendor/shop for every meal (and you eat one portion) you could easily get away with less than $5 a day/$150 a month. Less if you cook at home. But if you'd like some western stuff a couple times a week, you're looking at over $300 depending on what kind of western food you're getting. A Vietnamese street meal might cost $1 and a hamburger might be $10 if you're looking for specific numbers. That's for one person. You're looking at $40+ for 'dates' at nicer western places. Unless you're eating western stuff multiple times a day, buying for all your friends, and taking a lady out to fine dining all the time, you probably won't exceed $500 for food. At least I didn't and I loved to get sushi/burgers all the time and took my boy toys out pretty often.