I absolutley agree i have been on several installs where i have seen problems not related to the work i am doing and have reported them back to the client eg insect infestations ,slow leaking pipes , smell of gas etc after reporting these problems the client often trusts you more as it can save them money in the long run.
I see myself not only as a AV installer but a solution provider if my customer has a problem and its within my capability to resolve it safely and legally i will.
After reading several posts in this forum i am sure most of you do the same its worth your while to be nice
as for charging more as ian schatz said dont take on any jobs you cant do safely but a bit of muck didnt hurt any one as long as its clean!!