I believe the intent has evolved over time.
Pre-jail, I think it was fun for them to have a pet retard that they could tease without him catching on that he was the butt of the joke. Maybe they thought they could make some cash off of him, but Chris was really past his prime by that point anyway.
While he was in jail, he was very easy to manage since the criminal justice system was doing all the heavy lifting. All Praetor had to do was sort his mail and act as a gatekeeper
Post-jail, I think it's a lot simpler. Caden puts Chris up in his house and takes his cut of the tugboat as rent before Chris gets a chance to waste it. Everybody wins* Chris gets a place to stay -- that's no small feat for someone like him. Could you imagine him trying to shop for an apartment on his own? And Caden gets a little revenue stream with a permanent tenant who isn't going to cause too much trouble -- he's not going to throw wild parties or try to rip the copper wire out of the walls. Selling gravel and medallions is just gravy,
*except us, of course