While there is competition to become a delegate for the main chain, there will be plenty of demand to run delegates for the sidechains.
Thank you for your answer; however it is
earning Lisk I am interested in, and since it's almost impossible to become a delegate of the main Lisk blockchain, can you point me to a sidechain which will allow me to earn Lisk for securing it?
You will probably have to wait a few months for opportunities to run delegates for sidechains. It is a good time to set up a delegate to run on the testnet so you can gain experience. Also, it will depend on the sidechain as to whether they reward delegates in Lisk or their own token, which would need to be exchanged for Lisk or other currency of your choice.