Okay, say your group wants to sell their starship...

[rinku]

Coming in a little late, not sure if it was bought up earlier, but wouldn't the first step be... talk to the bank?

If I want to sell my mortgaged house and purchase a more expensive house, the bank is usually OVERJOYED to help out with that process, as long as it's clear that you will be able to keep up the repayments.

They do not care if the old house is in need of repair.

They do not care if the purchaser is getting a dump, even if they are financing the buyer's new mortgage (although you can be sure they will do a thorough valuation).

Contract is signed, they get paid.

Ka-Ching.

 

[Condottiere]

The thing about banks is, they want to be sure they hold your testicles in the palm of their hand, if you aren't in the class that actually doesn't need loans, but find it convenient as a tax write off, or that it's cheaper to borrow, than self finance.

 

[rinku]

Well, the pretty generous standard ship mortgage arrangements have always suggested a degree of banking regulation. Or possibly an accord reached between the old Vilani megacorps after a few centuries of financial warfare, back in the olden days.

No one wants a Fourth Great Financial War.

 

[Condottiere]

 

[ottarrus]

Example: a merchant musters out of the service with a Free Trader with twenty years left on the mortgage. After a fairly profitable five years, she wants to move to a larger ship.

How would you, as the Referee, determine a reasonable sale price that they might expect? How difficult would such a sale be to arrange? And how long would it take? Any suggestions?

If they mortgage with the same bank, it's fairly easy. The bank would LOVE for you to start all over again with your payments.
It's more complicated, requiring some Broker and Advocate rolls, if you try to sell to a third party. What's more, unless they're buying and selling on the same world as a branch of their banking institution, it can take a couple of months to get that done. And that's two months of no income... or at least, not enough income to make two more payments on Ol' Wulfy.
Another thing to remember is that when they sell their old ship they're only getting one-quarter it's estimated value...
But yes, with planning, luck, and good skill rolls it is absolutely possible to 'trade up'.