I'd be willing to bet your mom is just mortified about the idea of you getting a tattoo. The only way you would get hepatitis is if the tattooing needles were contaminated. As long as you go to a clean, reputable tattoo shop, you have nothing to worry about.
Short term complications are basically just infection. If you keep the area clean and follow the proper after-care procedures, such as using ointment and allowing the site to breathe, you should be fine.
Long term complications, in my opinion, are really just limited to regret. Once it is healed up, you really have nothing to worry about.
Back to regret...make sure that you get something that you're 100% happy with, and will be happy with for the rest of your life. I have 3 tattoos, one on each forearm and one on my wrist, which I got in my early 20's. I'm now 28, and I regret getting 2 out of the 3. Now I'm looking into getting laser tattoo removal, which is very painful and expensive. If I had it to do over again, I may not have ever chosen to get any tattoos at all. Just something to think about.
Brian