Hi there
I am currently in my 5th year living in Singapore - my husband is here with the US government. I agree with the above - it is very safe & clean, but I have definitely seen trash & there *IS* petty theft - low crime doesn't mean no crime! BUT -- I have never felt more safe, in general. My 3 kids wander the neighborhood (near the American school) without me worrying.
As far as where to live -- it really depends on where he'll be working or studying - he'll want to be fairly close. Depending on if that is near an MRT line, he could also look at apartments near an MRT stop that connects there. The MRT is efficient & not too expensive, which is good. Most other things here, though, are CRAZY expensive. Hopefully he's not a big drinker, because alcohol (and cigarettes) are heavily taxed. Hawker center food is cheap, but most restaurants are very expensive. Housing, too, is pricey. It's likely he can find an apartment share or something -- look on Craigslist, sites like that. For a short term thing like this, a share would be best. Maybe a long term rental on AirBnB or something? I don't know. It is crazy expensive though, especially depending on location. We live almost in Malaysia (because we want to be close to school) and our first house here was almost $8000/month (SGD, so about $6000 US?) for a 4 bedroom townhouse. This is what Singaporeans consider WAY out in the suburbs, "so far, lah!" The market has dropped a ton & we're now paying $6500/month for a similar home in the same area.
If he has money to travel, there are SO many places that are a short (cheap) flight away - Thailand, Vietnam, Indonesia, Malaysia. Tiger, JetStar & Air Asia offer cheap flights all the time.
If he'd like to get in touch I can try to help or put him in touch with a college student I know who spent a semester here & might have some better "young people" insight into the island
Message me or feel free to ask more questions here if you'd like