I'm not familiar with Harbor Freight products. I don't know if that would be a reliable nailer.

If you do decide to go out and buy your own nailer, you will want one where you can control the depth.

On decks, most of the frame is done with nails. The decking surface however, is better with screws. Are you also doing the decking surface with nails? If you do decide on that HF nailer and are nailing the deck boards, that nailer won't be good because it has no depth adjustment.

If you are going with a composite decking surface, you can also use deck clips. There are no surface nail or screw lines showing with clips, other than your first board. (Clips aren't good for wood deck surfaces)

If you feel you may have other projects coming down the road, it may be worthwhile buying your own nailer. Maybe with your own nailer, you will create more projects.

Do you have a decent compressor that can power a framing nailer?