Original: While Mike often does things at the expense or detriment of his housemates, he rarely expresses the sort of open hostility that the others do, and seems to  cause them trouble only when it benefits him, rather than out of sadistic joy.
Simplified: While Mike often does things at the expense of his housemates, he usually doesn't show the sort of open hostility that the others do, and seems to  cause them trouble only when it benefits him.