Let's say I am spending 250 USD to mine a coin of worth 330 USD, selling it immediately doesn't give me a big profit. If I am selling the same coin for 500 USD then thats a good strategy.
(amount spent on mining per coin in FIAT) : (Value of the coin)
when you get a good ratio convert the coin to FIAT.
Actually most of mining sites require an initial deposit for you to deal or to mine a specific coin. And we could hide the fact the if we are going to choose to sell it early , could not earn more or we could also loss a part of our initial deposit. So the best thing to consider to do is to save at first and then look at a way for you to actually deal with long term investments so you could have a profit with the used of the coins you've mine.