This planning session is hereby called to order!
I need to sort out the trade-in facility. When you buy a ship, you might end up stuck with it especially considering how long the lease is. You are only allowed to lease one ship at a time (this limitation is very likely the right thing).
Anyhow, you need to have some way of getting rid of the ship, converting some of the money you have put in back to assets. The logical thing is that some way or another, you take the ship you want to trade-in to the ship seller and they give you a lower price. The other way is you could sell them a ship you aren't piloting; but this feels silly from the players' perspective.
Maybe what will happen, is in the ship seller you can ask about a trade-in. If you do that, then some flag is set and the deals that are worked out include the trade-in value of the ship, and work as a trade-in. You see it's kind of annoying any other way because you still want to be able to choose financing, and it's just lots of wierd, pickly code. And further, what happens if you want to trade in your current, non-leased ship? You should be able to trade in a ship whether or not it has a lease, lease is just a special condition. So it gets annoying. But if I basically set a trade-in flag, and attach that to all the deals as I am generating them, it should basically work and make sense.