At the current hash rate It takes (very roughly) about 100 kh/s to consistently mine one block per day. From there you can easily work out that that it takes about 14 kh/s to mine one block a week and 3 kh/s to mine one block a month. Each interval can stretch out due to luck to about 5x the average (very occasionally longer) or of course you can mine multiple blocks in that time period if you get lucky.

Alternately, at any hash rate, it could all be about fun or supporting the network, or because as other comments pointed out, even pool mining will only give you tiny payouts anyway, which are also less efficient to use (due to high transaction fees when spending coins received as many small payments)