Two routes: one server or several Mini-PCs
Route A is a used 2U server (Dell PowerEdge R730/R630, HP ProLiant DL380 Gen9) for 250-450 euros: many cores, often 128-256 GB of ECC RAM, great for running lots of VMs. Downside: loud as a hairdryer and, depending on the CPU and BIOS settings, roughly 80-150 W at idle. Route B is two or three Mini-PCs or thin clients (Dell OptiPlex Micro, Lenovo ThinkCentre Tiny, Intel N100) as a Proxmox cluster: 200-400 euros together, quiet, often under 15 W per node. For a first homelab in a living space, Route B is usually the smarter pick; go with Route A only if the server can sit in a basement or utility room.
Planning ECC RAM and storage
If you run ZFS or TrueNAS, ECC RAM is a real advantage against silent bit errors. Used DDR4 registered ECC (RDIMM) is cheap: a 32 GB kit often runs 30-50 euros. Note that RDIMM only works in real servers with a matching platform, not in Mini-PCs or desktop boards (those need unbuffered DIMMs or SO-DIMMs, usually without ECC). For storage, used enterprise SAS drives offer plenty of capacity per euro and are built for 24/7 use, but need an HBA in IT mode (LSI 9211-8i, or the equivalent Dell H310, roughly 20-35 euros). If you want it simpler, run used SATA drives straight off the board. Always check SMART values after buying (power-on hours, reallocated sectors) and keep important data only in RAID/ZFS with a separate backup.
Networking: a cheap managed switch
As soon as you want VLANs, a separate management network or link aggregation, you need a managed switch. Used, an 8- to 24-port gigabit model for 20-60 euros is plenty (e.g. TP-Link, Cisco SG, HPE/Aruba). Old 19-inch enterprise switches are often dirt cheap but loud; for a cluster in a living space, pick a fanless smart-managed model instead. 10GbE is a luxury at the start and costs extra; for a first lab, gigabit is almost always enough.
Do not forget power costs
The purchase price is only half the story, since a homelab runs 24/7. At around 0.25-0.30 euros/kWh, every continuous watt costs about 2.20-2.60 euros per year. So an old 2U server idling at 120 W costs 260-310 euros in power per year, more than the hardware itself cost. Three Mini-PCs drawing 40 W together land at around 90-100 euros per year. Over three years the loud server quickly eats an extra 500-700 euros, which often makes the efficient option the cheaper total package.
Example budget under 1000 euros
Efficient Proxmox cluster: 3x Mini-PC/thin client (about 120 euros each) = 360 euros, RAM upgrades 60 euros, 2x used SSD/HDD 80 euros, managed switch 40 euros, used UPS 60 euros, cables and odds and ends 40 euros = around 640 euros, with headroom for the first upgrade. Power variant: used Dell R730 with 128 GB ECC 400 euros, HBA 30 euros, 4x SAS drive 120 euros, switch 40 euros, UPS 60 euros = around 650 euros. Both stay well under 1000 euros and leave room for the inevitable follow-up purchase.
