It comes down to your personal situation.
Investing a small amount of money to transform a decrepid PC into a stable but lightweight litecoin mining rig is all very well and good but it is unlikely to generate much in the way of income. Factoring in the start up cost and continued electricity for running it and it becomes less of a viable option.
The ones that seem to make money with this mining is those that have at their disposal the computers almost good to go (little money upfront = more gain later on)
Finally the mining itself is not a quick process. It takes a long time to mine one coin and even longer to amass any sort of "cash in'able" amount.
I personally would advise againts it. There is too much of a grey area, and the currency itself is volatile.
Just a bit of trivia, I recently read an article about the whole mining and in it was an interview with an anonymous miner. His job position was head of IT at a school and this enabled him to utilise their PC's for mining when they were not being used (A legal grey area). This was viable to him because he had it all readily available for little to no cost, and he had numbers on his side aswell. Despite all this, he was still only averaging 1 coin a week.