I'm big into prize ships. I've never let the players build a ship from scratch. That would take decades anyway. Even ships that are all blown to hell would be easier to salvage, assuming their back hasn't been broken. Look at some of the published adventures. Into the Maw has a grand cruiser as its prize. I never did like FFG's assumption that being in space for millennia somehow degraded a ship. It's a vacuum. Only something running into the ship is going to cause it damage. It's unlikely that all the systems are worthless. Something survived. I let them replace the broken parts and refurbish the rest. In addition to the grand cruiser, Into the Maw also has a somewhat scuttled merchant ship and two Wolfpack Raiders that try to jump the party. It's likely they can capture one of the raiders, if not both. The merchant could be towed back for repairs.
In The Emperor's Bounty a Lathe-class cruiser is the prize. Sure, I'd let the players salvage the ship for some profit factor. They could, however, forgo the PF and tow the ship back for repairs.
In Dark Frontier there is a Merchant ship (I used a Vagabond) drifting without drives. The players helped fix that problem and recruited the Captain of the ship to work for the Dynasty shipping colonists to the system in question and bringing Cold Trade items back to Footfall. This was an Endeavor that required them to find colonists, negotiate with the Kasballica Mission, establish xenos-tech "mining" bases, and provide security for those bases. After they completed the Endeavor, the Merchant, Penance of Iocanthus, ran the trade route for them, hence a Profit Factor. There were also many more ships in the same system, and after some searching the party found a somewhat intact Viper-class Scout ship that they towed back for repairs. Now they carry some spare Geller Fields with them wherever they go so they can tow ships back to port without an obligatory "cleanse and purify the ship of warp creatures" Endeavor after towing the ship. They also carry power cables to drape to the hulked vessel from theirs just in case of power failures.
Now we are playing Whispers on the Storm (the players are becoming veterans of All Things Yu'Vath, and they really hate them, too). There are tons of ships in that scenario, though they are mostly system ships and I don't think I'm going to permit any salvage, though they can always go back to the Yu'Vath Fortress in Dark Frontier and search the space hulk for more ships.
Anyway, that's my two cents. The players have now played through 9 different endeavors, are mostly Rank 3, have a small fleet of 4 working ships, 3 more ships being repaired at various drydocks (including their Grand Cruiser), and 3 colonies (which we've used some of the Stars of Inequity rules to flesh out). We've played almost a year (we only play once a month, except December, for a 4-6 hour session). Their PF has gone up about 25-30. I do keep track of both real time and the players' time perspectives, so it is possible they might some day attempt to have their own ship built, but I've discouraged it and the players aren't too upset about it, though they are a bit impatient about that Grand Cruiser, which I have to constantly delay (I don't intend to let them have for a very long time, probably about the time the campaign is ready to end….give it to them for the climax).