Of course, if I found that constructing a boat was beyond my abilities or I didn't have enough time to work on it I could always buy a similar boat instead. I've seen decent ones around the same size starting around $5K, so that wouldn't hurt the bank too bad.
Yes, there are some decent $5k boats out there that can be had for sailing not too far from shore. But a $5k boat for sailing around the world....hope your life insurance is paid up. When you really start looking into boats, you will find that boats built for blue water (middle of the ocean) sailing, come with a much higher price tag and there are reasons for it.