When building a DIY outdoor wood furnace, some things to consider are:
How large of an area are you heating?
Hot water or forced hot air?
and How much money will be required to pay for materials?
Many DIY outdoor furnace plans require buying materials new which can add up quickly.
JunkYardBoiler.com has an eBook and DVD course that focuses on how to build a DIY wood furnace using recycled parts that can be easy to find. It comes complete with resources and a support forum if any questions come up.
Check out Junkyard Boiler.com to learn more