...Unless you can get a screaming deal on a GPU or something, I think you would be hard pressed to find anything for sale that will pay itself off in under 6 months, even with free electricity.
Yes it seems like all the miner manufacturers these days price for about a year of mining to make your original investment back. But a lot can happen in a year: more efficient miners released for the same algorithm, your miner breaks long before the year is up, coin prices crash, etc... Doesn't seem worth buying anything anymore.