Just remember CO2 only costs about $12 to fill the bottle after you get one.
You should be able to get a used bottle for $80 and a cheap regulator for $30.
I haven't priced a a regulator with an electric solenoid yet, so if you know how much post it.
It is a lot easier doing it that way but I understand if you can't afford to. Sometimes people think it's more expensive than it is so I thought I'd throw some numbers out and see what you thought.