I second Model Car Mountain. When I quit building a little over 15 years ago I sold most of my truck collection to him. I’m not sure if it was Model Car Mountain then but it is the same guy. I named what I thought was a reasonable price for us both at the time and he paid cash. No hassle of shipping or checking in on EBay. Yes, I have now purchased more kits than I had when I sold out. So much for giving up model building.
I have also sold on EBay without issue too other than the time it takes.