Its ok, do what you want. My first MMJ grow experience was hydro. I started with 1 plant though. I was successfull. Hydro needs to be monitered on a daily basis. If you are only growing 4 plants you dont have to use a res, but if you would like to, a 5 gal bucket should be fine. Easch plant bucket should be 1/3 to 1/2 full of solution at all times. Make sure you use bubble stones in your buckets to keep the roots oxygenated. If you are making your own buckets, as I did. You will need to put some sorta way to know the level of water in your furthest bucket and res., if using a res. Otherwise you need it on all buckets. I am currently growing 12 under 2 x 600w HPS, come March I will be going down to 6 under 2 x 600w. I would say you would need to keep them on a monthly or maybe even a bi-weekly, turn-a-round. Just depends on how personal you say it is. Yield also depends hugely upon how much and what type of lighting you are using. If I was you I wouldnt go any less than a 600w HID.

Good Luck!