While creating user the security admin should get approval 
to create that user from the Project Manger. The 
particulars like lastname of the user, type of user, 
validity dates etc are required. Now u can create user.

first thing, u need to have access su01 transaction.
if the system in which we r creating user, is connected to 
CUA, then it is necessary to check if we can create user in 
child. while assigning roles, in role tab, progi,e for that 
role should be generated and user comparision should be done

While creating the user we have to know the following 
details:
1. System
2. Approval from linemanager
3. Type of user (Dialog or service etc.)
4. Roles to be assigned.
5. Validity of th user.

1. Manager Approval
2. System name in which user to be created.
3. User Last and First Name.
4. User group.
5. Validity date
6. Role with proper approval
7. User Type
8. Decimal notation.

The following fields are necessary for creating a a user.
1) System name along with the client number.
2) Last name.
3) E-mail address, so that password is sent to user after 
user is created.
4) Validity end date for contractors.
5) User group.
6) Roles(not mandatory. General role are provided by 
default if not mentioned)
7) Approvals from BSC and line manager is a must.

My answer is there are NO issues to create user in a SAP system.
It will be a different scenario if they ask what info do you
need to create a user in a SAP system. ;-)

The question is not properly framed in the first place.