****army help****?

i have some problems maybe someone can help me out i want to go to the army but mom disapproves and told me that i needed her permission like cuz i'm her only son and i dont know if thats true??? and i wanted to go for like sniper training like where would i start with that??? and is there like a certain amount of time need to be spent in the army i would be willing to do 8-10 years but i dont want to spend my life there??? and what age do u need to be to join the army??? thxs devin