Had this happen to me twice and both times I didn't end up with the bike.
I told a friend that I was looking to replace my norton (which I had just sold) and wanted another 70's bike. He told me his father had an old bike that hadn't run in years. I told him I wasn't looking for a project but I would give a call anyway. I spoke to the father the next day and told him that I wasn't ready to pay more than $500 for any project bike and he was ok with it. So far neither could tell me what kind of bike it was, the father and son were clearly not riders. Anyway so I get to the house and he rolls the bike out of the shed - a 1970 Ducati 750 GT!!!!!!. I tell him I'll take it but he needs to come up with a title (this was back in 1995, didn't know about title services). The bike turned out to be his brother's who dumped it in his lap before trundling off to vietnam. Anyway he called his brother to get the title and his brother came over with it. When his brother saw the bike out in the driveway the deal was instantly off. I offered them $2000 for it but they wouldn't budge. When I left they were still stairing at it in the driveway.
The second time one of my brother's friends saw my cb750 and told me his father had one just like it stored at their grand parents house. I went and looked an it was a 1969 diecast cb750 in candy red. Once again I told him $500 and he agreed. The trouble was it was in the back of the garage and I had to wait till they moved all the furniture out of the way. Two weeks go by and I call them and it turns out that they moved all the furniture and rather than call me they pushed it to the local bike shop where they were offered $300 and took it. I called them idiots right on the phone and hung up. Never spoke to them again and the kid avoids me when he sees me now.
the moral - don't wait fo sentimentality to kick in. Show up with cash in hand and move the bike that day. If you have to wait for a title take the bike anyway.