clone/veg room question

hey all some of u may of read my other post... i orderd my stuff and just waiting for it 2 come but i had a question or 2 on my veg/clone room....

i cant seem 2 figure this out and i havent even bought anything or thought of anything so this is completely up in the air...
(i want 2 use t5's inless there is somthing else i should be using) but yea anyway

my room will have

- 3-5 mothers
- 20-30 clones

questions

1.how many lights will i need.. for example (4 40w 40'' t5's)
2. how big should i make this room(i can make it small or as big as 5ftv5ftx10ft room)
3. will i need 2 use any ventilation for this room?

... dunno if this matters but i read that u should let yr plant grow till 2/3 of its final high b4 putting it in flowering room and im looking at for 80-100g a plant dry