Generally, a reseller account will provide you with most things you need. Virtually all cPanel providers will have PHP running on the server.
What you may find useful is a billing system, like WHMCS or Clientexec (among many others). Some reseller hosting providers will give you one of these for free. Others will sell it for a smaller or lager sum. Generally, it will be quite a bit cheaper than buying it from the developer directly.
For licenses, registration etc. you should contact the local authorities (tax office). Most accountants or lawyers should also be able to guide you.