[Samba] Help infomation to build the system as Microsoft Active Directory !

[Ha Minh Ai]

Dear Mr/Madam,
We have wanted to build the system for centralizal management: User
account, printer, policy, deploy softwares to client, manage update OS,
Single Sign On, ....
I know there have a same system as Micrsoft Active Directory, but we
haven't a lot dollars.
Please help me to answer some questions as the below:
 - How is the solution (*OpenLDAP + Samba*) on Ubuntu, RHEL/CentOS or SUSE
server ?
 - How many user can the system support maximum ?
 - Could i build the system include Primary Domain Controller Server and
Additional Domain Controller ?
 - Does Samba/OpenLDAP has cost-edition for enterprise ? If yes, what is it
different from free-edition ?
I'm looking forward to supporting from you. Thanks so much

Best regards,
Aihm