Before buying any carrier for your baby please ensure it is right for you. Carriers currently available on freecycle who's safety is dubious at best include the PREMAXX.
Please look at the following independant research done into "bagslings" http://babyslingsafety.blogspot.com/  
For more information or help with babycarriers join babywearing.com or a similar forum for help & advice.
Or drop me a line :)