Yeah the odor will be quite strong. I live in a one room apartment on the second floor of an apartment building. At the end of my first grow, I could smell my ONE plant from when I walked into my building, not to mention my apartment! Really depends on your exhaust. If that exhaust fan can clear out the whole basement in 5 minutes, it might be ok. I'm just thinking that it is such a big space, and with the fan that smell with blow around all over the attic and COULD leak into the house. If your growing some real dank, you might even be able to smell it venting outside.

You know that you will need to invest in ventilation, so when you do, just get a carbon filter and you can just "plug it in" with the rest of your setup. Better safe than....