Dunno what downside there could be, if you have the time and a use for
the lumber, and a way to safely transport it. If you are not going to
use the lumber immediately, you need to have a place to store it out of
the weather and flat so it does not warp and bow out of shape. (Happened
to a friend-- he tore down a house for the lumber and by the time he got
ready to use it, a lot of it was no good). Also, most of those "tear
down for the lumber" deals specify that you take all or none, and often
have a set time frame that it must be completed within. FWIW, I
know a guy who built a pretty good sized 2 story house almost entirely
out of materials he scavenged over about a five+ year period. Among
other things, he got about 2000 sf of maple flooring about an inch thick
or more from a gymnasium that was being torn down. I've seen the outside
of the house and it is beautiful. People who have seen the inside tell
me it is absolutely incredible. Go for it
if you want, but start with something small first. Good luck Larry