Hi inline300
I am not well versed on the minimum cost to get into this hobby. Others, I'm sure, will help you with that. Get connected with a flying club. Many teach you to fly free. At our club we even supply the trainer plane and all equipment. To wet your appetite for creating your own design, here are some of my own designs, all SPADS:
http://www.rcuniverse.com/forum/m_80...tm.htm#8007330
http://www.rcuniverse.com/forum/m_34...tm.htm#3476218
http://www.rcuniverse.com/forum/m_43...tm.htm#4379145
http://www.rcuniverse.com/forum/m_73...tm.htm#7388836
http://www.rcuniverse.com/forum/m_70...tm.htm#7019698