It all depends on what you want to do?
After 20+ years of trial and error, I buy my Doors. (unless a customer wants otherwise.)
By the time you figure in all the expenses, $90-100 for a window, $35-40 for a GOOD lock, another $40-50 for moldings and the same for the rest of the materials, hinges, sealant, mistakes, blunders, hours of standing around scratching you head and the weekend or 2 it will take to do it, just to see if what you've done will work......Its a real coin toss.
I will say this, Manufactured doors won't leak, go in easy and the Lock always works.
http://www.ebay.com/itm/RV-Teardrop-Tea ... es&vxp=mtr
But if your looking for a Project, as some people are. Make them!
Happy Trails
Len