Whenever a Realtor calls our office and asks for a structural engineering inspection of a home, we take a deep breath/gulp and think about the liability that comes with this type of service. In our mind, a proper structural engineering inspection starts with mapping out the interior floor plans at each floor level, performing a floor level survey, inspecting the attic space to determine the type and adequacy of roof/ceiling construction, locating and determining all interior load-bearing walls, mapping out the foundation and main floor framing system from inside the basement or crawl space, then superimposing the floor plans atop one another and onto the foundation plan to see how everything aligns. This must be done in any proper structural evaluation because it provides the following information for the engineer to ponder:
1). The locations and magnitudes of any perimeter foundation settlement and/or interior floor sag; "is it a ¼ of an inch or 3-inches of sag/settlement"
2). The load-path transfer of roof, ceiling and floor loads down through the home and onto the foundation;
3). The sizes/spans of rafters, ceiling joists, floor joists, main beams and locations of foundation piers/posts;
4). The alignment or misalignment of stacking rooms atop beams and foundation supports.
In conjunction with a study of any crack patterns that might exist inside or outside the home, 
this type of inspection gives the engineer all the information that is necessary to define the structural adequacy or inadequacy of a home, and develop solutions to correct any problems that might exist. Once everything is on paper, in the form of CAD drawings, the engineer can explain to everyone involved if problems exist and explain why a repair is or is not needed.
If you think that any foundation repair contractor goes to this great length of study, before making repair recommendations and establishing costs for repair, you'd be fooling yourself. And to even think that a foundation repair salesman has the structural knowledge to perform a proper structural engineering inspection and assessment may be ludicrous. Unless a salesman has grown up in the construction business, he has no idea about the interaction of a home with the underlying soils/geology, how to assess foundation design/performance, how to assess floor/wall/ceiling/roof design/performance and how to assess the design/performance of connections between the various components. Hopefully, they do. We certainly hope you think this is important.
Probably the most significant difference between an engineering inspection and a free estimate for repair from a local foundation repair contractor is that the engineer has no vested interest in the repairs. He is not making his living from commissions earned on repair sales. He is objective, impartial and fair to everyone involved-seller/buyer/Realtor.
The critical thing to take away from all of this is, "What defines a proper structural engineering inspection?" We hope you feel that if every structural engineer and/or foundation repair contractor does not take the above-described steps, then you can't be getting a clear structural picture of the home. We hope you will choose an engineer who will go through this method of study to determine if a series of cracks or problems is truly a structural concern. It is ridiculous to simply throw large sums of money at some crack or group of problems via a foundation repair contractor, simply to make the sale happen, rather than spend the money on a proper structural engineering evaluation, especially if the repair costs exceed five to ten thousand dollars. The seller deserves this.
What does a proper structural engineering assessment cost?
It all depends on the size of the home. Naturally, the smaller and simpler a home, the less cost. A 3000 square foot, colonial, two-story home, with 1500 square feet per floor, 
constructed over a crawl space, for example, would cost about $2,000.00. This would consist of the inspection, generation of CAD drawings, compilation of photographs and CAD drawings, and the inclusion of this information in a written report, complete with recommendations for repair, if deemed necessary. This report could then be given to a host of repair contractors to bid on the same scope of work, should structural repairs be deemed necessary. No more getting three completely different repair proposals from three different contractors.
And this sort of inspection/report is perfect to provide to a prospective buyer, especially if there are minor cracks and separations inside and outside a home; or, more importantly, to simply establish that a home is structurally sound and free of construction deficiencies. For example, all of the cracks are cosmetic.