Drug business was booming post war. I think there would have been too much money involved for Michael to cease the political protection that the Corleone Family was providing. I think once he had eliminated the other Family heads he would have expanded his Family involvement. Behind the scenes and with dispassion but money is money.
On the other hand brothels weren't quite the money makers they had been because of declining mass immigration and loosening social standards. But we know that Fredo oversaw at least one brothel in Nevada. So I think Michael would have avoided the prostitution business in NY-considering it too little money for too much stigma.
"When the snows fall and the white winds blow, the lone wolf dies but the pack survives."
Winter is Coming
Now this is the Law of the Jungle—as old and as true as the sky; And the wolf that shall keep it may prosper, but the wolf that shall break it must die.
As the creeper that girdles the tree-trunk, the Law runneth forward and back; For the strength of the Pack is the Wolf, and the strength of the Wolf is the Pack.
| 
