it depends on whether you get the roller (just the rolling chassis) or the RTR package which includes esc motor and i think battery.
ebay by FAR is the cheapest. i got mine new for $349
no, you don't need to use the losi batteries. i use zippy flightmaxx 6S lipos, they are fantastic.
https://www.hobbycity.com/hobbycity/...0mAh_6S1P_30C_
check out my post here for the way i did my 8ights. it might give you some more help.
http://www.rc-monster.com/forum/show...07&postcount=9