I'm looking at getting a 1/2 cello for my son. My options are either rent a mid-end one for 50$ a month, or buy a very cheap one (there seem to be some online for 150$~200$). 

My experience with very cheap instruments is mixed: 

The cheap ~100$ guitars are usually so bad as to be completely unplayable. 

Cheap Keyboards and Electric Pianos, though annoying, are good enough for a child learner waiting to see whether they will stick to the instrument. 

If 3~4 months rent will buy me a new cello, I would just go with the cheap cello and wait later for when he grows tall enough for a full size to buy a quality instrument. 

But am I worried that the super cheap one will be like the cheap guitars, so bad that they can't be played correctly. Is that the case? Should I just rent instead?