ma on shan to hkust will be troublesome by public transport. even by car, that's about a 30 minute drive assuming no traffic. think horizon suites has a shuttle bus to the green line, to choi hung or kowloon bay. if you do that, then train to lei yue mun, transfer, train to hang hau, minibus to hkust -- that's about an hour, not including waiting times. i think there's a bus from ma on shan to sai kung, then minibus to hkust, maybe less than an hour.
anyway, my point is, while horizon suites might be good for people living along their shuttle buses' route, too out of the way for everyone else.
i seem to remember coming across a few people in the sai kung / clearwater bay area willing to rent out furnished apartments (probably middle floors in village houses) for less than 7k. just search diligently on google. sorry, i would do it for you, but too long (2 days) without my 141 fix.
http://www.gohome.com.hk/english/home.asp is a good place to start. most agents won't want to do less than one year lease, i think. but shouldn't be too hard to find someone who can help your mate. the trouble with many of the agents on gohome is a lot of them don't answer e-mails, just phone calls.