After starting your own game, join your own syndicate.
Select your branch. Go to "Employees", and select "Security
Guards". On the right, you can select a Thug, Burglar, etc.
Select your Thug, hire him, then look at his stats. You can choose
to beat him until his health refills. Do this a couple of times,
then send him on his own mission. He will have an icon above his
head, like an anvil or something else, and he will not take damage.