It does not matter when you start mining, it matters when you sell the coins. So, mine, sell small amount only for electricity and HODL! 
This man speaks the truth. The biggest profits have never been made by buying and selling immediately, they're made by picking the best of the best and mining / holding. There have been times I was mining at only $20-30 per rig per day (even $0 when mining new launches), but with hindsight the amount was 4-5x that and more.