Buying or selling YouTube channels is a severe TOS violation which will end in account termination for both seller and buyer if caught by YouTube Admin. Please read the excerpt below.
"The following restrictions apply to your use of the Service.
You are not allowed to:
- access, reproduce, download, distribute, transmit, broadcast, display, sell, license, alter, modify or otherwise use any part of the Service or any Content except: (a) as specifically permitted by the Service; (b) with prior written permission from YouTube and, if applicable, the respective rights holders; or (c) as permitted by applicable law;"
Channels are part of the YouTube Platform; and therefore part of the YouTube Service. Normally I'd report a post such as yours for advertising a service which violates YouTube's TOS; but this time, I'll only warn, and wait to see if an admin sees this thread and chooses to take action.