A .40-sized glow engine like the Super Tigre G-40 will cost you about $49.99. An equivelant brushless electric power system can be purchased to fly the plane with similar authority, it will set you back about $250 to $300 for motor, speed controller (ESC), and LiPo battery.

If you need to go cheap, go glow. If you need to go electric, spend a little bit extra and buy a real airframe. Balsa flies better. You can purchase a Ready-to-Fly electric trainer with a brushless power system and radio for around $299.99 plus batteries:

http://www.hobbico.com/airplanes/hcaa12.html

Good luck and good shopping.