A lot has to do with where you're growing. Is it a house, or an apartment? How close is the nearest neighbor? If I have 30 or 40 running at a time, there are certain weeks when I can definitely smell them in the house, but not at all outside. However, I have a neighbor who must have a lousy filter, because some nights when I go outside for some fresh air before bed, I can smell his plants loud and clear. Haven't figured out yet which one it is, but it's someone within a half block or so.
If you live alone, in a house, you can usually keep the odor contained without any trouble. Whatever you do, don't put a window air conditioner in the same room as your plants, because it will exhaust the air from the grow room directly outside. Anyone walking past the AC unit can smell the grow if you don't have a good carbon filter. Personally, I have decent ones but not top of the line, because I never allow anyone in the house for any reason. I don't mind if it smells a bit inside. In fact, I kind of love it.
If you're only doing ten plants or so, electricity probably won't be an issue. What are you thinking; 600 watts probably? That's just a relatively small percentage of most people's monthly bill. The one thing you do want to be aware of, though, is whether your electric company uses "smart meters" - the ones that show your exact electricity usage for every minute of every day. Running a grow with a timer stands out like a bonfire in a dark room with those fucking things. Suddenly, your usage jumps 600 or 1000 watts at exactly 12:30 PM every day, and drops 600 or 1000 at 12:30 AM every day. Any moron can see at a glance what that means. I hate those fucking things.
