It's fine for the first 4 weeks or so, after that, (when the bud starts to thicken up a bit) do not spray them anymore. It creates too much unnecessary humidity in the grow room and around the buds.
During mid-late flowering you want lower humidity (rH 40-60%) and NO water on or around your buds if possible.
Misting/spraying with water during veg is fine, do it all you want, and if you want to continue to mist during the early stages of flowering, that's fine too, even add a weak foliar feed if you want, but come mid-late flowering do NOT mist/spray your plants with water. It will only raise the chances of complications (e.g mold/fungus) showing up.
Cheers.
P.S - You don't need to add CO2, especially if you can't afford it. CO2 is in the air, just like oxygen, as long as your plants are getting fresh air, they're getting enough CO2. CO2 is something you might choose to add in an advanced set up if you want a few more grams at yield. Me and some buddies have all tried using it, and all found it a complete waste of time, effort and money. It's simply not necessary, and not worth the money for the little benefits it provides. Some people love it and swear by it. For me, it simply cost more then it would to buy the extra few grams it helps yield. - *From personal experience and my opinion*
