1. For central office to have at least small server room – dedicated isolated room with at least consumer Air Conditioner [better japanese – about 1500000 mnt + installation fee]( when you use only RACK without server room – too loud, physically not secure even for locked RACK [anybody can hit or collide with RACK and shock damages hard drives], too much dust which will clog all fans and as consequence rise of temperature, fan speed, even more noise). Size is at least 2×2.5 meter to place RACK and be able to go around it, room door better to place exactly in opposite of RACK door – easier to slide long equipment into RACK. The cheapest room is from gypsum boards.
2. If budget is tight, instead of real servers, buy reliable good Dell Optiplex workstation with improvements like — 16Gb RAM, i7 cpu, two or better even 3-4 SATA drives, or if budget allows – SSD drives, preferable also with full vPro/AMT kvm support, or at least Standard Manageability (not so good as Dell iDRAC or HP iLO, but better vpro than nothing)
3. use it as Hyper-V server (each SATA for one/two VMs – otherwise sluggish).Esxi and others is too capricious to device drivers.
4. don’t be too shy and limited – start using AD/Active Directory (in my opinion when number of computers become more than 5). AD can be used even when you have problems with licensing and so on.
5. don’t save money on UPS. As i see too many companies use very good, expensive SmartUPS, but don’t care to configure graceful shutdown.Especially it’s true and actual for server, and moreover for virtualized servers or DB server.
6. don’t forget about backups. There are a lot of free and cracked very good solutions (for example Veeam BR) to backup your VMs to old desktop computer with extra HDDs thru network by schedule.