Sean, About 10 years ago I did some research into growing my own tobacco. I bought some seeds and a book online and gave it a shot. I did not make out well because I kept forgetting to water the plants or left them outside during a storm. So I can not tell you that much about growing them. Other then water them and keep them safe :)
In my research I found some of these facts. (remember this info is about 10 years old)
In 1933 the US government included the â€œtobacco programâ€ in the Agriculture Adjustment Act. The program limited the amount of tobacco that could be grown in the US. All farmers growing tobacco at the time were given quotas that they could either fill or they could rent there quota to bigger growers. The program also allowed for regular citizens to grow there own tobacco for personal use. The amount a citizen can grow was set at 1/10 an acre per year. In 1/10 acre you can grow 400-500 plants. A mature plant will yield about 5 oz. or cured tobacco. So if you planted the maximum amount of plants and they all produced 5 oz you would end up with 156 pounds of tobacco. A pound of cured tobacco can make up to 400 cigarettes so you would be able to grow enough to make 62,400 cigarettes or 312 cartons.
It takes one pound of tobacco to make 400 cigarettes Commercial cigarette makers us 1 3/4 pounds of tobacco to make 1000 cigarettes. So you can see that there is about 3/4 pound of additives and fillers used in commercial cigarettes. Check this link to see a list of additives added http://www.tobaccoseed.co.uk/additives.htm
I would have to say that if you were going to smoke/use tobacco in any way it would be much safer to grow your own, that way you know that there are no crazy additives added.