Ken started selling [off] his goats when his oldest son stopped sending monney to him.

Is 'off' optional?If needeed, what information does it provide?


I don't think that "to sell something (to someone)" and "to sell something off" are interchangeable.

The Oxford Dictionary says:
sell something (to someone)
to give sth to sb in exchange for money

sell something off // sell off something
to sell things cheaply because you want to get rid of them or because you need the money
Thanks Takoyaki! I get it now