Works better if you at least start them inside and place in a sunny window to get them established. I'd say until at least the third node. I moved some autoflower plants outside early like you mentioned last year and it took almost the entire Summer to finally get them to catch up with plants that I kept inside for about three weeks.
I picked up two small T-5 fluorescent grow light for cheap last year to use in a smaller tent for seedlings and it worked well to get five plants established this year. $32.00 each. You could probably get by with some CFL bulbs in a cheap worklight fixture for less just to establish your seedlings. Move to a sunny window during the day. I had a plants get to 12 inches and really bush out just by doing that for a month last Spring until it got warm enough to move outside.
Probably depends on what temperature is like where you are. On days that reach 50 degrees Fahrenheit during the day right now I put plants outside where they get 6 or 7 hours of direct sun and they do fine when put inside under a small two bulb T5 light inside, it also hardens them up for when I put them outside permanently..My nighttime temperatures are in the 20's currently so I have to bring them inside as the sun goes down.
If your nighttime temperatures are above 60 degrees Fahrenheit you will be fine, but in the first few weeks of a seedlings life the plant can be destroyed in minutes by certain bugs like a beetle larvae that looks like a mean caterpillar. I had one on an outdoor plant last year that was already packing on buds and it was eating its way through the plant rapidly. On a seedling it could kill the seedling in minutes.
