In my opinion, right now is a terrible time to invest in a lot of new mining hardware. Current generation mining hardware (.5-.6 W/GH) has been available since October, and next generation hardware with twice the efficiency is right around the corner and should be available within the next month or two.

If you buy now, your .5-.6 W/GH farm will be quickly obsolete. Also, given the current price of BTC, best case you're looking at at least 9-12 months to get your money back depending on your overhead costs. If your overhead costs (rent, electricity, utilities, labor, ...) exceed 10 cents / kwh, you have no business running a mining farm.

If you believe in BTC, and since the price is currently low, you could buy some BTC directly and hold it as a hedge against rising prices and use it to buy more efficient gear once it is available.

If the BTC price spikes, your hardware purchase just got less expensive. Hardware manufacturers will charge as much as the market will bear, so a spike in the price of BTC will make all mining hardware more expensive.

If the BTC price tanks further, it makes zero economic sense to invest in mining hardware and you dodged a bullet.