This (reply) may be late in coming but if so, maybe it will help someone else, ref: subject line.
When shopping pre-owned coaches last year we used RV Inspection Connection.
They have a nation-wide network of NRVIA certified inspectors and some of which are likely nearby your location or that of the coach your interested in. If not, they can travel (for a small additional fee). In many cases, beyond being technically qualified, many of their licensed inspectors are fellow enthusiast who are highly experienced full-timers and do the inspections to supplement their income. All RVIC inspectors are licensed & certified to include being bound by no conflict agreements which further protect their customers by ensuring they (inspectors) are not affiliated with the sellers such that what you get is a truly non-biased professional assessment by a qualified inspector who is working in your interest.
Money well spent we say; RV Inspection Connection's reporting format includes detailed component by component condition assessments, "think nose to tail / top to bottom inside and out", documented in the form of written observations/findings that include condition ratings, the reports can be anywhere from 30->60 pages including photographs. Not cheap mind you, but well worth the relative investment when considering the cost of the coach your considering. Depending upon the size (and complexity) of the coach your interested in the RVIC inspections can take anywhere from 1-1/2 to 2-days and will require the coach to be connected to both shore power and water/dump facilities to include pre-hook up prior to the inspections so that they can inspect the related systems & equipment operation, i.e. refrigerator, washer/dryer, macerator, etc. etc..
We used them last year when searching for a late model DP and had them inspect two separate late model pre-owned coaches (one in Dallas(dealer) and one in Asheville, NC (private seller)). The inspections we purchased included all fluids sampling and laboratory analysis. In both cases, the detailed reports we received from RVIC led us to "walk away" from those deals owing to issues found of which we did not want to have to deal with, i.e. high phosphates/calcium in the cooling system, and contaminants/particles found during lube oil analysis leading to further questionable maintenance history on both. Also and noteworthy of mention; in both cases, the sellers claimed they were not aware of the exisiting problems found by the inspectors.