My first advice to you is to visit Overgrow.org. From my experience, 18 hours of light a day during the Vegetative (height) period does a growing plant some good. When it comes to the Flowering (budding) period, the amount of light drops down to 12 hours within a day. As for a time frame as to when to change from one to the other, I cannot say it's definitely this or that since a plant's ability to grow and your ability to nurture does play a major part in when it's ready to switch over. I myself change after a couple of months.
5 plants to start with may not be the greatest idea if you've never done any kind of growing before. 1 or 2 can keep a person busy enough. I'm not sure what you're asking when it comes to your question about ventilation and the fans. If you're referring to keeping the stench down, that's not going to do it alone. If it's just a question of ventilation, as long as it's fresh air and the fans aren't blowing the plants over, you should be fine.
DON'T FERT TOO EARLY! I'd wait to fert after the second week and that's a very small amount when I do so. When to water is a little tricky but most people just lift the pot and determine whether it needs to be watered or not by its weight.
As for the type of fertilizer and soil to use, there are too many to choose from. Miracle Gro works for me, although I feel their soils are prone to being attacked by white flies, spider mites, and the ones that look like miniature millipedes.
Hope this helps