Consew 206Rb-3

[hooked]

I have access to buying a Consew 206rb-3 for $700. However, when I went to test it, the bottom thread got tangled due to not holding on the the threads properly. While I was there we cleaned out the bobbin and hook, and tried again. This time the botom thread would not thread. I left, and the owner said he would look into it. Since then, I've learned there is a safety clutch on the hook. Could this cause the bottom thread to not engage? Also, he said i could buy as is for $650. Are these machines easy to service for these problems? Would $650 be woth the unknown risks? What could the cost be to get a machine like this into working condition? Thanks for your help.