I have a blog sitting on a sub-domain, and I want to know is it possible to sell such a property, or do I have to migrate it to a .com domain? TIA for your input.

Like a blog hosted on blogspot or wordpress? You could potentially sell the account if it's getting decent traffic or making money. But a more likely situation is you could sell the content as articles, just export it all. You're not likely to make much money from just selling the content.

Moving it to its own domain and selling it as a stand-alone site is a much better option.