I am completely new to Bitcoin mining. Now, I have some pretty basic questions. Please excuse me if you've heard these questions many time before.
If I buy an S7 and run it here in Hong Kong, according to profitability calculators, it should make around $220 per month, minus pool fees. Now, if I buy 10 of these, then I should make around $2 200 per month, not so? Now, at $1 650 per unit, that should pay itself off in around 6 months, give or take. Thereafter, I get $2 200 per month.
That sounds pretty good, is there a catch?
yes there is a catch called difficulty.
If more and more "miners" running because they have the same idea like you, this difficulty will go up.
and therefor you will get less BTC every 2 weeks..
so, the hint is, before buying hardware, inform you about Difficulty and how mining work
Exactly what fronti said, PLUS your calculation should also be based on:
1) the current price of
BTC (which might vary)
2) the current block reward (which will halve mid 2016)
3) the current KWu price you pay (which might change)
4) the current difficulty (like fronti said)
5) the fact that you'll be able to mine 24/7 without any interruptions
6) you might be able to overclock your systems, but maybe you'll have to underclock them to keep them running stable
7) luck