Ideally it would be best to split this into 2 machines. This would be preferable for several reasons.
1. Downtime: with only one machine, your hash rate drops to 0 during maintenance.
2. Redundancy: if you have a single component fail, all of your miners will go offline. Since you will be co-locating this service somewhere outside of your immediate control, this could be a big issue. Lets say your miner goes down in the middle of the night. Will your friend be willing to go let you into the server room at 1am? With two, you only drop to half of your hashrate.
3. Cheaper components: to go from 1000w to 1200w you are looking at a 95euro increase in price. That is almost the cost of another 850w PSU.


Since this isn't going to be a machine you are going to have immediate access to, I would go with two cheap motherboard with 3 PCI-e slots (buy these new). Two cheap CPUs (buy used if you can). 2G of the cheapest ram that will work in each machine would be way more than enough (buy new). Cheap HDD, borrow and old one from someone or just run off flash drives (borrow if you can). Then 6 GPUs, 3 in each. The most important thing is to get them online as quick as you can. Buy locally if possible, 3-4 days tied up in shipping is 3-4 days you aren't making money.

-SteveA