I would not buy that channel, and I would keep building the one you already started. When I started my first tutorial channel, I got the same pattern, lots of views and very few subs, and the fix was not a trick, it was the end of the video. I now finish every tutorial with one clear line, I say if this fixed your car, hit subscribe so the next repair shows up for you, and I put the same line in a pinned comment. That one change moved my subs from almost nothing to a slow steady trickle, because people subscribe when they know what the next video will help them fix. For your question about registered users, I would not lock a tutorial behind anything. I keep my tutorials public, because most of my viewers find me from search when their car has a problem, and a locked video never gets found that way. If you want a video only for a small group, I would make it unlisted and share the link only with them, and I would keep the main repair videos public. On the bought channel, I would be very careful. Even if the subs are real, they subscribed for the old videos, not for BMW repair videos, so they will not watch, and your watch time will fall fast. I have seen a channel lose its reach that way, and YouTube can also review a channel again after a big change in topic and owner, so the monetization is not safe just because it was approved before. I would ask the seller to show you the last few months of analytics on a screen share, and I would look at where the views come from and how long people actually watch. If he will not show that, I would walk away and grow your own channel with one repair at a time.