I would have concerns about a 30 year dbl. wide too. The floor will probably be MDF or particle board. Anything that has spilled/leaked/urinated on it in the past 30 years will have caused it to dissinegrate into saw dust. Vapor barrier is most likely gone, as others have said.

If you do decide to inspect it:

1. DO NOT remove the vapor barrier if intact. Remember that we are performing an inspection based on what is available to be inspected. Remove any of the vapor barrier and you might as well take out your wallet because you will be replacing it.
2. I wouldn't go onto the roof, too much risk there. If you break through and damage their perfectly good roof you will be hurting, physically and financially. Inspect it from your ladder.
3. Disclaim anything that is not visible and able to be inspected. ie. limited roof inspection, underflooring in-accessible, roof cavity is not accessible due to ceilings, etc.
4. Remember that ther may very well be aluminum wiring.
5. PB supply piping and ABS drain piping will probably be present.
6. Place in bold print at the beginning of your report and throughout the systems area of your report that the home is beyond it's life expectancy and anything and everything should be expected to break at any time.
7. etc.
8. etc.
9. etc.

__________________
Integrity Inspection Service, LLC
www.irsindy.com
(317) 345-1828