To enable Remote Management from the command line, enter the following into Terminal
sudo /System/Library/CoreServices/RemoteManagement/ARDAgent.app/Contents/Resources/kickstart -activate -configure -users ARDADMIN -access -on -restart -agent -privs -all -allowAccessFor -specifiedUsers -computerinfo -set1 -1 "INFO1" -set2 -2 "INFO2" -set3 -3 "INFO3" -set4 -4 "INFO4"
sudo /System/Library/CoreServices/RemoteManagement/ARDAgent.app/Contents/Resources/kickstart --configure -access -on -privs -all -users ARDADMIN
You will need to switch ARDADMIN for the account you wish to give ARD access to.
INFO1, INFO2, INFO3, INFO4 refer to the fields located in System Preferences, Sharing, Remote Management, Computer Settings
To enable SSH for one specific user, enter the following into Terminal
sudo systemsetup -setremotelogin on
sudo dseditgroup -o create -a USER -t user -u USER -q com.apple.access_ssh
You will need to change USER for the shortname of the user you wish to grant SSH access to.