Ok, motobecane bikes are not KHS knockoffs. Both designs come from Astro, which is a taiwanese catalog frame maker. Basically these companies (khs, motobecane, etc) don't spend money on the R&D for frame designs, and instead slap their stickers on Astro designed bikes. Astro owns the IP/frame design and companies license them. The only reason I know this is because my previous DH bike was a KHS dh300 and I was researching the frame design and came across the above information.
Motobecane bikes are made by a company called Kinesis Industries. From what I understand, kinesis also makes GT, Santa Cruz, Diamondback, and a bunch of other bikes. Basically these companies don't own their own manufacturing facilities in Taiwan. In this case it's owned by Kinesis, and Kinesis churns out bikes for all sorts of companies that are sold over here.
Under no circumstances would I buy a DH bike from a rental fleet. These bikes get thrashed beyond belief and are not maintained properly. Best bang for the buck is definitely purchasing used. Many filthy rich groms need new DH bikes every year. Check the pinkbike discount rack at the end of the year you'll find some amazing gems.