For hosting, go with Cloudways, there you can host multiple applications on one server. As per requirement, later you can scale it. In my experience, it would be easy to manage.
Very first I would ask, Do you have a team or are you going to managing self?
I think multiple websites requires regular maintenance and updates. For one person, in 24 hours it's not easy to maintain 100 sites. So, better would be; start with small, step by step.