If possible find an unlined drum - even pay extra for one!
I built a new one last summer & paid for it to be shotblasted inside & powder coated the outside - cost me £80 + £20 for the drum.
This is my new one
It is a lot of fun to make & you can make them relatively cheap - however I have now bought an electric Bradley smoker & cooked a load the weekend (only 2nd time I used it
They also do a 6 rack version & 2 rack version (2 rack are less than £200)
Any Qs or help, then ask away - or look on
http://www.bbq-brethren.com/forum/ for a ton of info!