Go for an AEG man. I wouldn't recommend you starting off with a bolt-action or any kind of sniper platform, its a money pit to get them to shoot accurate and with the consistency you'd need. You'll be more accurate with an AEG simply because you can put more rounds downrange.
Batteries will die eventually, its inevitable. Its good to have a spare when you go to games if one that you use goes dead. At the last game I discovered that both my batteries for my m4 don't seem to hold shit-all of a charge anymore...so now I need to buy new ones. You can prolong your battery life by getting a good charger.
Take a look at the retailers. There are several decent models of guns available for under 400 dollars.
Guardians of Asgaard - KF25 -
Primaries: LCT AS VAL, LCT AKS74UN, VFC M4 CQB Mk2
Secondary: Latino heat, TM Glock 17