Wow this forum is having some issues in posting - let's try this again....
Any ASIC hardware for mining SHA-256 (Bitcoin) won't likely pay off at today's prices/difficulty, nor in the foreseeable future. See this explanation, or there are several others out there -
http://www.holynerdvana.com/2013/12/bitcoin-asic-roi.htmlIf I was to only throw $500 into mining (and not buy and holding coin) I would get an ATI GPU card and place it in a computer I already have. You can use this as a starting reference of what cards to look for:
https://litecoin.info/Mining_hardware_comparison Find some scrypt mining profitability calculators, and run the numbers on what cards you can afford. un-shortened link to calculator:
http://www.coinwarz.com/cryptocurrency/?sha256HashRate=0&sha256Power=0&sha256PowerCost=0.1000&scryptHashRate=600.00&scryptPower=400.00&scryptPowerCost=0.1000&sha256Check=false&scryptCheck=true (Coinwarz.com)
Here's some really rough numbers:
Say you find a deal on an ATI card that can do 600 kh/s, and the card and whole computer consumes 400w.
If you mine at Multipool or Middlecoin, etc that switches coin mined based on profitability at current exchange rate, then you may be able to get $7-$10/day, with power at $.10/kWh it would cost $.96/day. Not a bad turn on investment for power consumption, but you won't pay for the card for 55-83 days, at current exchange rates. If mining profitability goes up or down, this can change wildly. I have in the past month seen time-to-payoff times vary from 20 days to 120 days, assuming then-current exchange rates and not holding for speculation of higher cashout rates.
YMMV, I hope this helps.