Sean explained it well -- very well in fact.

Grasshopper, with all due respect, this is not something you'll pick up from watching a YouTube video or by getting an answer on RemoteCentral forum.

I've been messing enough with networks to know what my limits are.
While I use few subnets in my own house because of my 300+ IP devices, several DHCP pools, etc., there is no way that I would just 'take over' what you're describing. One wrong command or inter VLAN route and you could crash the network or worst, open it up to a hacking attack.
900 units = 900+ pissed off people when they can't get on the net.