"My last question is how is the resale on a home-made boat? " Zero, or damn near to it.
By all means look into hull design and handling, there are a number of good books out there that go into that in good detail. Until the advent of PC power, hull design was very much a black art as much, or more so, than a science. The problem is that you are dealing with multiple variables and they all interact dynamically. You can, for instance, design a static hull with the centers of effort, balance, gravity, etc. all neatly laid out where you want them. But now, watch the waterline change as the hull picks up speed, forms a bow wave, and squats in the water. And then as the boat starts to heel over--all the hull dynamics change.
Design your hull in 3D so that you can match all the variables at all the angles of heel, with various wave motions (and make it cut through the chip instead of slamming, and make sure it doesn't hobbyhorse) AND under different sail trims...and all of a sudden you've got a HUGE task, one that was essentially impossible before mini-mainframes and still is going to bring your engineering software to its knees.
I'm not sure that anyone--even the pro designers--has software that can account for all that and still generate hull lines, simply because the cost of developing it would be so high.
Ask folks if they have ever sailed a boat which is so well balanced that it can be trimmed with just the sails--and then will hold any course, by itself, with no hand on the rudder, for at least a half hour. Most sailors will tell you flat out "No way!" but there are some few hull designs that actually hit that sweet spot. Ask the folks who designed them, and they will all say it tooks lots of experience--and then they were still damned lucky.
So when you buy a boat, you are also buying the designer's reputation and the known performance of the boat. And THAT has far more resale value than anything else in the boat.