You probably could do it all with one switch/router, but running that many home runs across floors is a pain in the ass, plus, you might be getting close to cable run length maximums. If I were you, I'd have one core switch and an edge switch for each floor. That way you'll only have to run 3-4 home run cables. Or you could make it a loop and run STP on the backbone network. That way there would just be one cable per adjacent floor, plus one from the top to the bottom, and it would be able to survive a single cut in any of those cables. Or lose the top-to-bottom cable and the STP and make it non-resilient.
Using a separate switch for each floor is likely to be significantly more pricey for the hardware, but probably not as much as it would first appear. Switches usually have 12, 24, or 48 ports. You probably don't want to try to squeak by with 48 ports for a 50-person building, so you're already looking at getting two switches, and getting four or five smaller switches is still going to be more expensive, but not as much as it would initially appear, especially one you factor in labor costs for cable running.
I think the midrange for switches these days is probably SMC. I can't really think of any other manufacturer; everyone else seems either too low-end or too pricey for what you're doing.
As far as configuration goes, I'd definitely consider isolating each network so that the residents can't snoop on each other. This would probably necessitate using switches that can do 802.1Q VLAN tagging, which will increase the per-switch cost, as you'll have to get "managed" switches.
I'd definitely bring these options up to your customer. Don't say "I can do this or this", ask them if they need the different rooms' networks isolated, and how much resiliency they need, etc.
As far as a router goes, I'm not sure. TrendNet and Netopia come to mind as mid-level players. I think Cisco actually makes some not-outrageously-priced SOHO routers that would probably work for you. You might even look at the firewall market. Something like a SonicWall probably makes sense, too, and might provide some nice value-add for your customer, with the residents being able to VPN back in.
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Bitt Faulk