an e50 is fucking indestructable. and you can rebuild it yourself.
im building a magnum like this myself. i started with only a magnum frame, and the side covers and trunk piece. i then bought chrome maxi EBR forks and a chrome swingarm from treats. Then i got some chrome Maxi shocks and threw them on there. It sits realy nice and low. they call this type of setup a mini magnum.
Then i got some clubman bars and other odds and ends. Im going to try to get some 5 star mags and an e50. Then im going to put a 70cc athena reed vaulve kit and portmatch it, tune the clutch, expansion exhaust, etc. hopefully itll be pretty awesome.
Im spending a lot of money because im using a lot of new parts and performance aftermarket shit. You could buy used stock parts, or even used performance parts and save some money though.
Good luck and have fun.