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Hey, so I found this (expensive) place to live that has a fixed-cost electricity. I initially didn't want to live there because of the price, but since the utilities are fixed-cost, I'm kind of considering it now.

I was wondering if anyone else has done this and I was wondering what the best kind of rig you could build for the cheapest to get the most amount of coins. I was hoping to net around $200/mo (with the cost of the rig taken into account) from this to offset the expensiveness of the apartment.

Back when GPUs were used and margins were thin, (e.g., around Dec. 2011, and then again Dec. 2012 right after "halving") the only ones making money were those who paid the least for electricity.

ASICs are soooooo  much more efficient on power and so few in production yet that the cost of electricity is a tiny fraction of the ownership cost.  For example, today the cost of electricity for a BFL Jalapeno (ASIC) running a full day is about twelve cents.   That does 5.5 Ghash/s, and earns at the current difficulty about $20 worth of coins (at the current exchange rate).    So the cost of electricity is less than 1% of the revenue generated from that electricity.     A person with free electricity mining using an ASIC has relatively no advantage over a person paying a high rate for electricity.  

If you are thinking "free" electricity gives justification for buying GPU-based hardware, think again.  ASICs are shipping hard and fast (as charted here: http://bitcoin.sipa.be/speed-lin-ever.png ), and the last of the GPU's days (for mining Bitcoins) are nearly over.  It could be less than a month or two that even those with free electricity will shut down their GPU rigs (or switch them over to an alt currency that GPUs are still useful on).  

The fastest ROI on GPU is ~80-90 days at today ROI...thats assuming you have the power and slots to run a PCI-E Radeon card.


7870XT or 7870 Myst cards for ~$200-$240 usd will have the fastest ROI if you get them to hash ~500-530mh/second (bitcoin mining).


7950 is a good choice too.

I would go with Sapphire or MSI if GPU mining.

4x7970 + MB + CPU get 800W

i hope with this you can cal. total.

MB - cheap asrock ~ $47
CPU - intel ~ $60
RAM - 2GB ~ $15
:)

Let's say OCd 1k, maybe 1.25k psu.

I don't understand if you can make $20 per day from a simple machine what is stopping someone from buying tons of them and making 494949$ per day?

Maybe this?

http://bitcoin.sipa.be/speed-lin-ever.png

and that means? sorry I am 11

I'm going to assume you are serious, or at least somewhat serious. 

That graph means that the difficulty of mining coins continues to rise at a VERY fast rate.  The higher difficulty rises, the same hardware mines fewer coins over time.  For example, the last difficulty adjustment (which happens about every two weeks) was 28%, so the same hardware is mining 1/4 LESS coins than what you were able to mine with that same hardware less than two weeks before.  With this ASIC hardware (that is expensive and in very limited in availability) continuing to come online, difficulty will continue ot rise and probably at an ever-increasing rate.

Soon, GPU miners will find it difficult to be profitable, similar to what happened to CPU mining after the first GPU miners were written.

Good luck.

yes that is common sense. however that doesn't mean 2 machines doesn't mine double the coins 1 does (or close to it)

True 1 -> 2 machines is a substantial increase...
But as you get more and more machines, adding one additional shrinks that additional machines income proportionally
Imagine if you had a farm of 10 machines, adding one more is only a 10% increase
If you wanted the same ratio as going from 1 -> 2 ... it would be 10 more machines to the 10 that already exist.

and that is fine...? still making tons of extra money

Ok, I see what your saying, w/ unlimited power - yeah you could purchase enough hardware for a 100GH GPU farm and be quite profitable for a while. Yeah you can, but expect it to become ur fulltime job for maintenance on the entire farm. You would have to find a place that could take that power draw - standard house wont really do for a massive farm.
Just plug the numbers into a calculator like http://www.coinish.com/calc/#
Which calculate based on a predicted diff increase curve. You can see the hopeful potential profit you can make.
Expect it to take quite sometime to get ROI on the initial investment
Figure you can sell all the parts for about 50-60% of what you bought them for, given they all still work fine =)

I just ran some quick #'s... if 100GH in 7970's cost about 50k USD - and diff & price stayed the same, you would barely / never make ROI, even after selling stuff for 60% initial cost.
Now, you would make ROI if u hoarded the mined coins and hoped they went to insane value someday =)

It's not "extra" money until you cover the initial money paid for the machines. Your question involved buying a ton of machines.

Now factor in the difficulty that was explained to you above. Imagine you get $20 today. And then half of that tomorrow: $10. Then half that: $5. And on and on. You will eventually get to numbers so small that they will never add up to the initial cost of the investment.

Now my half-per-day was just an example for simplicity sake, but if you punch numbers into some of the calculators around here it isn't far off (if the difficulty is exponential).

also, you should consider the initial investment, gpu aren't free

It is also easy to start tripping the breakers in a regular home when you start spending upwards of $10K on GPUs.

How many amps of free electricity can you practically get anyway?