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.
If you are going to have the same scenario where you are going to used a money or to deposit an amount of fiat for you to earn or to mine bitcoins the thing you need to do is to analyze every transaction or decision you are about to do. Because you could not earn if you will just see bitcoon as a short term investments for you to sell it without depending the sections on the current price or rate of bitcoins value.