Question: how can i connect three computers on lan at minimum hardware cost?? 

Answer: get 3 network cards (NIC). They are around $5. Get a autoswitch (you can get a Dlink DSS-5+ for $15 on the net). And get 3 Cat5e cables to connect with the switch (they are 3-5 $ each). Often computers have a NIC on board, so check first (control panel - system - hardware - device - mangager - network adapters) if you need a NIC on each pc.
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