You're stepping into choppy waters my ambitious friend. Especially when dealing with an apartment grow, stealth (while maintaining efficiency) is normally the most important thing to consider. I really HATE to discourage someone from doing something so responsible and beneficial as growing their own Cannabis, but from the sounds of it you are going to experience major ventilation problems if you aren't able to find appropriate equipment in your area. It is almost inevitable that you will have somewhat exposed ductwork or venting equipment, and the fact that you are concerned about your friends noticing the grow is troubling. You would want to find the ONE area that nobody EVER goes to. If this is impossible due to space restrictions in your apartment, you will need complete co-operation and understanding from all parties entering your place, so as to not jeopardize the security.
HOWEVER... this usually results in people talking about it to others.... so...
It brings me back to the original discouragement.

You really want to have your stable environment IN PLACE before you even germ a seed. That way it's just plug and play and :jointsmile: (in a perfect world :greenthumb
If you are unable to achieve proper ventilation AND have problems keeping it a secret... you may spend all sorts of time growing problem plants AND have to eventually scrap it all when everyone keeps asking "WTF is THAT?"
It's not worth it to keep stringing along shitty nugs until you get busted.
So, with THAT said... you can find fans at Home Depo or Lowe's that work okay... but it depends on how much air you need to move. I was able to get away with a 6" inline duct fan from Home D outside the box and have it connected via flex duct. But yeah... NOBODY HAS EVER SEEN IT, even though it looks like a space ship that a kid would build.

Sorry if that doesn't help. Just be safe :hippy: