3 main panels. WAS appartments.

The building was used as 3 apartments using three meters and three 100A panels. Now, it’s being sold as a single unit home.
Q; Can it be sold with three panels and three meters as a single unit.
Q; Will the buyer get stuck with the upgrade cost?
Thanks, Bill O

No idea but one service is cheaper then 3 services .
If Mine and I was not going to rent any part of it I would be changing to one service .

The new owner will probably want to ditch two of the meters to avoid the monthly service cost.

What upgrade do you think is necessary?

I remember doing some handyman work and a lady was converting a duplex back to a single unit. She had service and panels combined to one. I can see the meter cost reasoning but…
Wait; Can one meter lug three service entry wires? I’m pretty sure these panels have no auxiliary lug at the main connection.

It might be possible to jumper them together. Some will depend on the load calculation.

The property should be served by a single drop/lateral regardless of how many panels are on the building(s). The conversion to a single meter should be pretty straight forward.