if you are not selling shared hosting and you have server administration knowledge, webmin is a great free control panel to make your life easier

For linux control panel

Cpanel, Plesk, Direct admin,webmin with virtualmin are ok

For windows

Plesk, Dotnet panel, Hosting controller, Helm, Ensim are ok

Many free panels are there for both linux and windows but not much effective for an example Lxadmin is there for linux which have less support from any one

from many providers you can get cpanel license for $20 a month