For your first rig I would try to buy a gaming motherboard (MSI Gaming 7) I believe supports 6 GPUs and a better quality PSU (eVGA or Corsair). This way if it does not work out for you, you can either convert it to a gaming rig for your own use or resell it. The GPUs you will probably have no issues reselling, but again stick with the better name brands that are in demand.
Right now for mining Ethereum or Zcash, I would also recommend either the RX470 or RX480 series cards. Since these are still new, the resale won't be much of an issue at all, you can probably get 75-80% back should all else fail.
Start with one, maybe two cards. Add cards as you get more familiar with how it all works.
I also agree 100% with this advice. Buy a mobo that can support 6 cards like you want, but there is no need to buy all 6 GPUs day 1. Get it setup and running and once you know your values, such as hash-rates, power draw, equipment costs, you can better calculate if adding the additional cards will make sense or not. Most of us started out this way and not just jumped in with a fist full of dollars and no real plan.