Noob questions

Hey everyone. I'm an aspiring home brewer, looking to get into the hobby. I've read a couple of books and a lot of forum posts in various places, and have a very good idea of how to proceed. However, I still have a few questions that I have been unable to find answers to. I am hoping someone (or someones) will be able to answer these for me:

1) When doing the primary fermentation, how much does it smell around the area where the fermentation is taking place? My fiancee has a very sensitive nose, and if it smells markedly like yeast every time she walks by the closet then it's going to lead to unhappiness.

2) I like to experiment. One of the reasons I'm interested in brewing isn't so much so I can make clones of beer I can buy, but to make beer I can't buy or easily find. The more experimenting I do, the more I risk making stuff that comes out nasty. And even if (no, when!) I make something good, a 5 gallon batch is still 48+ 12-oz bottles, which is a lot for a couple of people who don't drink an excessive number of beers per month. Is there any reasonable way to brew smaller (eg. 2.5 gal) batches using extract kits and specialty grains? For example, split a 5 gal extract kit into 2-2.5 gal batches that proceed in parallel? When using a secondary fermenter, does the amount of airspace at the top of the fermenter matter? For example, if I put 2.5 gal into a 5 gal secondary fermenter, would all that air end up oxidizing my beer?

Any insight into these questions would be appreciated!

Many thanks.

I have only noticed a smell with my really strong smelling beers, my mead is making a good smell of yeast honey in the room its in. most beers wont stink it up at all...

you can always scale down a recipe from anywhere..beer tools has a function that will do it for you.. you can get smaller carboys then 5,6,7 gallons. I have only 6.5 gal ones and have not worried about the airspace ...not sure how much the air would oxidize with all that left over space. I would say just make sure your brew is colder then the ambient air temp in the room. If it is warmer you will create a vaccuum while it cools and suck more air into the secondary

Smaller extract batches are not a problem. Very simple to scale down a recipe. As for smells, it depends. Some hefeweizen yeasts give off an extremely strong sulphur smell. If you have a garage or basement, I'd recommend doing your fermentation there, esp. if your significant other has an issue with the smell. Not all beers are going to have a strong fermentation, so you'll have to see what her tolerence level is.

Good Luck.