I could do that, Zz, but I'd wind up pulling the stats from the books again, everybody would want to design their own ship...And we'd be back where we are now.

(For what it's worth: Hi.

)
---
But since I can see Zzyxzs and others glaring at me through their computer screens and willing their arms to reach through and strangle me after reading that...I'll lay out an example.
Take the Classique III from Arsenal, since we've used that to argue over.
Strip out the Luxury Amenities, you get...Oh, 10k.
Default, I'd say it looks like such. I'm at school, away from books, so these are really guesstimates based upon some Googling and guesstimates.
Length overall of 100 feet (30.5 meters)
Beam of 6 meters (20 feet)
Draft of 2 meters (12 feet)
Height above waterline, let's say 8 meters (24 feet).
These dimensional values are likely to stay pretty constant, really it's just to show what kind of scale you intend, making sure to take into account the
square-cube law (What? SR commonly ignores it in the height of buildings? Yes, I know that. But let's try to keep it in mind here.

) and such things, and give us all a sense of size and volume. I might use them later to figure out where the heck to dock the thing, and whether you can go down a river, but that's minor for right now.
---
These next numbers, on consumables, are more likely to change. Playability will come into account, as well as feel and general sanity.
Fuel consumption is tricky. If there were an easy way to figure out how tech had advanced to 2072 from 2010, I'm certain I have not found it. We used a useful metric of 2.6 km/L last time for the classique III, borrowing from Rigger 3 (which had 2.0 for the Classique) and advancing the tech a tad, and I figure that works for this go-round too. Generally, if you can find a similar vessel in, say, Rigger 3? Save yourself the work. Throw me the numbers and we'll work out something that feels right.
Fuel storage: Should really scale with fuel consumption, but keep in mind volume. For the Classique, a fuel tank of 500 liters seems more than adequate.
This works out, by the way, to 1300 kilometers range for a full tank. That may be a bit small - I can certainly see an argument for upping the fuel storage in the default tanks, possibly by a lot, because 1300 km range seems low.
Water storage is tricky. Karoline had a useful formula for water usage last campaign that we may as well apply here:
"Each person uses 118 L a week (Trolls use 125) and dishes/cooking uses 20 L/day."
Maybe dwarves would use less? But that sounds a bit odd, because dwarves aren't really that short by comparison, whereas trolls are huge.
Let's assume...10 humans/elves/orks/dwarves, 1180 L per week for all 10, then 140 L/week for common stuff. 1320 L/week, comes out to.
Let's say 12 weeks of water storage works for argument's sake, 15840 L of storage. We can up this, but I'm basically throwing out numbers to give us something to argue with.
So far as feel goes: When it comes to fuel, my gut instinct says "Get numbers that make it a concern, so that you can't just ignore it". Water, well. Even on a converted yacht, I want to maintain a sort of naval-ish feel. Shadowrunning is presented as kinda grimy compared to the ultra-cleanness that the trid makes it out to look like, and that's sort of the feel I want to go for so far as water usage goes. Water isn't in desperately short supply, but hey, can't waste it either.
For the record, I'm pricing diesel fuel at 5Y per liter at game start, and water at 0.2Y/liter. Yeah, water isn't free - because you'll be starting off in Miami, I checked with parents, who have a condo in Florida. Turns out that the South Florida region is basically in an unending drought so far as freshwater goes, and I don't see it getting any better in 62 years.
---
Still going:
I'm going to figure that you want everybody on the crew/passengers to have small single-bunk quarters, with a small bathroom (toilet, shower, sink, that's it) attached. My instinct is a sort of like a small single dorm room.
So let's figure on "This ship can carry 20 people in posited quarters." Sounds sensible for a yacht conversion, including crew and passengers. Probably a low-ball number, but it works.
You then get modslots per Arsenal, plus 1 because we removed Luxury Appointments earlier in the example. Cost of the yacht is per Arsenal, deducted from the 500k budget, but you get 10k back from the cost when you downgrade the living spaces. (One of my non-trivial considerations here is the loan. If I make it too small, you can't get much, or it becomes too easy to pay off. If I make it too large, it rapidly reaches a point where you can't functionally pay it off.)