Help! Buy bit miner

Me and my friend are wanting to enter this branch of mining Bitcoin ..
So far we have 1700.00 Dollars, but I'm seeing if I can blindfold me Radeon HD 5970x2 + Cooler Accelero Extreme III and also my HD 7970 .. to pick up a few more 2200.00 on aggregate ..
But not to generate profits of 20 , 40 , or 100 dollars per month , but a high rate of profit knows ..
We were thinking of starting on 1st Month with one of 120GH / s or 200GH / s ..

After arriving in this 120GH/se she spend a month working , considering that later this month it will generate something on the average 0.700 BTC / Month = $ 1005.00/Mês then would buy one of 200GH / s ..
Clear that this purchase of 200GH / s is an alternative only because that would buy it, would be one of 1Thash / s that currently give around 5,832 BTC = $ 3,969.38 reais that would be something like R $ 9,451.49 . .

This all was initially the case knows , since with these drops every 12-14 days you can never stop evolving in terms of hardware right , but I believe the average initial 2-3 months to correct this would be a nice start ? Well after buying the 120GH / s or 200GH/se buy him a 1Thsah / s will be much better since adding two months of work it pays the value generated what we spend on it (I'm considering this to calculate customs duty tbm . . ) , so in the coming months we could better and / or increase our machinery .

Because we do not want something to give a few bucks more , we want to create a lucrative income high , not to saying : " Ahh , the Bitcoin will live forever ...
But we will see in the right ..

Of course we have in mind that in the first 6-8 Months (No Minimum ! ) , We would catch anything that does not profit us know these values we would be converted into new investments of course , because once started, can not fail to evolve equipment time to time too right after all turns and moves will come out stronger and faster machines for mineirar and combat levels of difficulty coming to increase ..

So I would also ask if anyone knows the machines too and learn some link or site or store or website that I can buy them nee ..
Even better if it had the pick them up in Uruguay because to me it would go in one day and back the other lol , would be better in terms of spending too ..
But I need reliable sources , it is not every day that you spend 2 , 4 , or 10,000.00 thousand dollars on something to lose your money is not ..