I commend you for maintaining a polite and civil attitude after reading some of the responses on here.  Some people forget, or never did know, what it is like to be a young person starting out with limited resources.  Something like what you experienced can be a huge financial issue and leave you feeling pretty down.  A few words of encouragement can do wonders.  One word of caution is to get the opinions of others more experienced before saying anything negative about  someone you purchase a piece of used equipment from.   
Sorry about the experience you had but just consider it a learning experience that will serve you well in the future.  Most of us have had similar experiences in the past but we lived through it and it made us a better business person in the long run.  Wish you the best in the future.