If you're leery of giving opinions (as we all should be), use a disclaimer like the below. Vary it to fit each assignment. It will not save you from all repercussions stemming from bad advice, but it should make giving good advice a little more doable.
ASSUMPTIONS AND LIMITING CONDITIONS
1. Any legal description provided to the consultant/appraiser is assumed to be correct.
Any titles and ownerships to any property are assumed to be good and marketable.
No responsibility is assumed for matters legal in character. Any and all property
is appraised or evaluated as though free and clear, under responsible ownership
and competent management.
2. It is assumed that any property is not in violation of any applicable codes,
ordinances, statutes, or other governmental regulations.
3. Care has been taken to obtain all information from reliable sources. All data
has been verified insofar as possible; however, the consultant/appraiser can neither
guarantee nor be responsible for the accuracy of information provided by others.
4. The consultant/appraiser shall not be required to give testimony or to attend
court by reason of this report unless subsequent contractual arrangements are made,
including payment of an additional fee for such services as described in the fee
schedule and contract of engagement.
5. Loss or alteration of any part of this part of this report invalidates the entire
report.
6. Possession of this report or a copy thereof does not imply right of publication
or use for any purpose by any other than the person to whom it is addressed, without
the prior express written or verbal consent of the consultant/appraiser.
7. Neither all nor any part of the contents of this report, nor copy thereof, shall
be conveyed by anyone, including the client, to the public through advertising,
public relations, news, sales or other media, without the prior expressed written
or verbal consent of the consultant/appraiser -- particularly as to value conclusions,
identity of the consultant/appraiser, or any reference to any professional society
or institute or to any initialed designation conferred upon the consultant/appraiser
as stated in his qualifications.
8. This report and any values expressed herein represent the opinion of the consultant/appraiser,
and the consultant's/ appraiser's fee is in no way contingent upon the reporting
of a specified value, a stipulated result, the occurrence of a subsequent event,
nor upon any finding to be reported.
9. Sketches, diagrams, graphs, and photographs in this report, being intended as
visual aids, are not necessarily to scale and should not be construed as engineering
or architectural reports or surveys.
10. Unless expressed otherwise: 1) information contained in this report covers only
those items that were examined and reflects the condition of hose items at the time
of inspection; and 2) the inspection is limited to visual examination of accessible
items without climbing, dissection, excavation, probing, or coring. There is no warranty
or guarantee, expressed or implied, that problems or deficiencies of the plants
or property in question may not arise in the future.