How many miles is too few (not Longroof related)

So I've been shopping Crown Vics and Gran Marquis for an everyday car and the Gran Marquis are easy to find with low miles because they appealed to older people who don't drive much. I was kind of looking in the 2007-2008 range but I came across a 2005 with 39,000 miles. That's basically 3900 miles a year. I wonder if that could actually be bad. Wanted input from fellow old car enthusiasts/mechanics. I know my Roady had some leaks from sitting after the owner died but most of them fixed themselves after I started driving it regularly. Except for the transmission cooler lines. That was a real Niagara until I fixed it. Any opinions?

No downside. Change the fluids, drive it, enjoy it.

I just bought my 91 Caprice Wagon w 33k and it's had only 2 issues so far after 1k, a slight leak from the water pump which I then replaced. It was just at the shop today for a Trans fluid & filter change and to have the rear lubed /serviced since I didnt have any records of it being done and I was getting a weird sound/ knock once in awhile after being parked ...it needed a U joint, so they replaced both (fluids and bottom of the Trans pan were all clean when removed) . Drove it tonight and all is good.

It depends how it was driver. Can you ask the owner? My mom as a 1999 Civic with about 25k miles on it. She drives such short distances it never warms up the exhaust in the winter, so she'd had to replace the exhaust and a few rusty fuel lines already. Otherwise it drives like a new car.

Also check if it sat for a long time, and if so why.