In my opinion, total free hosting is a a waste of time and money because if you want to stop abuse and keep security in an acceptable level you need to pay for some software such as CloudLinux and CXE. But it does not guarantee that free client upgrade their services to paid one. If you don't try to consider security and let abusers do anythig they want, then even those free clients who was planning to upgrade will be lost because they will think your paid service is not better than free one.
A good idea may be to create a plan with very low resources and set its price to very very cheap even less than $1/mo but keep your working on providing security and reliability. In such a business scenario, those who need hosting for only trial, learning or doing their collage project will not bother from paying for that very low fee. And those who establish real and active websites, will go for upgrading to higher plan and keep their invoices paid as long as they see what they expect from growth of their website and your service quality. So by this case, you don't offer free but a service worth only a coin and you have opportunity to get more paid. If you can get a few hundreds coin-valued client, you may earn good cash.