If you are looking for something that is repairable and very easy on the wallet I would go with a Clone, also known as a Tokyo Marui clone gun, IE: Marui MP5 = $250, a clone with almost the same specs would run you around $125 if you know where to look. Clones are somewhat compatible with Marui parts so if something breaks and Marui makes it, most likely you can find the part.
Clone brands would include, Galaxy, JG, WELL, CYMA (my first clone), D Boys, UTG, KART and if anyone else wants to chime in on ones I forgot..... :-k
I shop on airsoftgi.com, or airsoftatlanta.com, try those out and let us know what you find, any other questions feel free to pm me or post it on here.... =) good luck