i'm not sure i completely understand your question. if you're looking for the cheapest brushless car look into the traxxas vxl's. if you're looking for the cheapest brushless system for a car you already own, look at tower hobbies at the new castle creations kit. its under 150.
Safest lipo's IMO would be the apogee's, they're actually Li-Mn Lithium Manganese and are way less volatile than most other lithium based batteries. Check out the puncture video they've got on their website. They ARE a little heavier but you pay for abuse that they can handle.
The wisest mind has something yet to learn. (George Santayana)