Having a tatoo will not affect your employment, unless it is visible during working hours. For example, if you work in a corporate office thats business or business casual, your usually not allowed to have visible tatoo's. It doesn't mean you can't have them, they just have to be covered.
Example, I have a friend i worked with for 2 years who's sleaved up both arms, when we are at work, he always has to wear long sleeve shirts.
Tatoos are excellent, as long as you understand why you're getting one. If you're going to be a retard football player and get barb wire around 3 quarters of your arm (most puss out because it hurts pretty badly on the inside), then you might end up regretting it. But if you get something that has some meaning to you, something you don't mind being remembered of on a daily basis, than i say go for it.