RO sign in houses. Calling 30yrs, joedavis and others who might know about this

I see the sign RO with a cross under it in some houses. A friend told me that the city paints this sign when a house is singled out for demolition. I saw a house with that sign that was renovated 10 years ago. It looks fine, new boiler, dry basement, etc, generic reno. The sheetrock in 2 of the upper corners is sagging a bit, but my architect (who saw it) said that this can happen after 10 years with these cheap renovations. What do you think I should do? After all, the owners got mortgages on this, so probably the house was appraised. Should I contract the services of a house inspector? Are there engineers that I can consult without going through an inspection process? With an verbal assessment, I will be ok.