Your joists do not look like they are pressure-treated lumber in the photo. Are they? If not, it's a bit of a gamble on their long-term performance, isn't it? I don't know where you live, but anywhere in the Rocky Mountains (as inferred from your screen name) will be subject to rain and (lots of) melting snow. If you're planning on flipping the property, so be it. If you plan on being there a while, you might consider applying some heavy duty preservative, like copper napthanate, to the joists before installing the decking.