Can I have multiple toll free or local number on the same account?

Yes, you may have multiple numbers point to one account. There will be additional costs for additional numbers.

How long does it take before I can use the VOIP Mailbox service?

FreePBX provisioning will take 2-3 days.  This involves activating the numbers and setting up the system for first time use. The PBX can be done in 1 day, SIP...