I’m always willing to help out a friend but I try not to put myself in the middle of things. If I knew someone who wanted to buy something a friend had, I would put them in touch with each other and step aside.
For an example, when I was a cop, if someone walked up and said they needed a tow truck, I’d give them the phone number of the vetted companies we used. I would of course call for them if they asked me to, but I preferred they called themselves.
Why? Because about 25% of the time it turned into some degree of hassle for me that wouldn’t have happened if they had just called the tow themselves. If I call, now I’m the point of contact. The middle man that adds no convenience to the transaction. “Hey this is mikes towing. I went to the address and the guy isn’t there.” Or “hey it’s been an hour and mikes towing hasn’t shown up yet. What’s going on?” Basically a million variations of the above that could have been handled between the driver and the tow company if I hadn’t been the one who called. It’s not like everyone doesn’t have a cell phone anyway.