From a DIY standpoint, it's not very practical. I've given some serious consideration (to the point where I've started creating prototypes in SolidWorks) into that and have run into a few issues, mostly hull construction issues.
The first issue is using wood. It looks awesome, super awesome. But it's a difficult to work with, it's very time consuming, and a lobor of love, which means you have a lot into it. So when you hit a rock and trash your boat, the loss is ten fold.
The second issue with fiberglass is that you need to have a lot of space to work in, and the initial investment of required gear makes it prohibitive if you only want to build one boat.
That being said.... if you want to save a few bucks and like building stuff, kits might be the way to go. You might want to try this if you want a synthetic boat. (note: this isn't a fiberglass hull, they explicitly say so on their site. Not sure if it's better/worse/the same.)
http://www.boulderboatworks.com/drift_boat_kits.php
Or a wood boat.
http://gregboats.com/pages/driftboats.html
Also, perhaps one of our insurance guru's can weigh in on this. I'm pretty sure if you buy a recreational boat, it's covered by your home owners insurance policy. However, if you build your own boat, I have no idea how that works. Might be something to give some serious consideration to incase something happens to you boat and/or the people on it.