Really really depends on the college as to what stuff they need/how much stuff they are allowed. I'd have to say that actually there's been a trend for less and less stuff. I was up in the mid-90s at a college where we had big rooms and were basically allowed to practically refurnish the whole place ourselves - rugs, pictures, chairs, futons, fridges, sandwich toasters, rice cookers, fairy lights, ornaments, giant blocky computers and printers, TVs, throws, cushions, candles everywhere, full sets of plates and cooking equipment, the lot - there was even a fashion for making your own curtains. My parents hated taking me up at the start of the term! I'm an academic now (at a different college....) but what students can and do bring has reduced a lot. Some of this is changing fashions and equipment and so on: computer equipment is much lighter and smaller, can watch TV on laptop rather than bringing one, etc. Some is increased rules on health and safety - my current college won't let students bring furniture, fairy lights, candles, soft furnishings, or their own kettles, fridges, toasters etc. any more for fire safety reasons. Some colleges have very small gyp rooms and the culture is to eat in hall; also Cam council kitchen safety regs changes mean that colleges had to remove ovens from most gyp rooms/student kitchens a few years ago, so they can cook less now than they used to. The students seem less interested in stuff now, too - they just don't seem to bring as much any more! Plus anything you need can be ordered cheaply online or from the supermarkets and delivered to the college nowadays - a far cry from the time when Cambridge had hardly any shops. I think the best option is to bring only essentials until he really knows what he needs and what the college allows. Plus first year rooms are often very small and term is short! Agree too that most colleges now rent out student rooms for conferences during the vac, so there may be little or no storage between terms.
Yes, easy to get a bike in Cambridge (don't forget helmet....) I also have never had a bike though. Definitely possible to walk instead, unless you're at one of the really outlying colleges. I have never ridden a bike here as (as LRD says) it is not a very safe cycling city and traffic accidents with bikes are very common. I've seen a few nasty ones myself, enough not to want to cycle at all (but then I don't need to get to outlying colleges/departments often)