Commercial inspecting is very different from inspecting homes from a business point of view. Before I give the client a price, I first find out what their expectations are, what they want to learn about the building. Most of my commercial clients are very experienced with buying commercial buildings and they know what they want. Others have no little or no experience so I guide them through the process.
Based on the information you provided, I would expect to charge around $400-500 for a typical inspection. Inspecting warehouses is about the easiest money I can make. It usually does not take any longer to inspect a 20,000 sq. ft. warehouse than to inspect a 2,000 sq. ft. house.
As an aside, there are certain things to be aware of when bidding commercial work. You cannot inspect certain items such as boilers, elevators, underground storage tanks, and fire protection in most states unless you are licensed to inspect them. Experienced commercial buyers understand that those will be extra charges. You may coordinate the activities of others as part of your inspection and charge a fee for the service. Often, the client will make separate arrangements for the items requiring special licensing. If they are covered by any of the FM member companies, those items will be inspected by FM. Even then, if you have experience working with FM your client may ask you to work with FM on their behalf.
We hear a lot in the home inspection industry about ASTM standards but my commercial clients are more likely to ask for inspections to be done according to FM standards; even if they are not covered by an FM company. The reason is that FM standards usually meet or exceed any other standards. A building that qualifies as an HPR can get insurance coverage at a very substantial savings.
In larger work such as high-rise office buildings and manufacturing plants, we are not generally called “inspectors” for the work we are doing. The more common term is “Owner’s Rep”. We may be doing more project management than actual inspecting.
As yet another aside, it is very common in the commercial inspection world to do work by Divisions. For example, many of the engineers and architects in my area know that my so I sometimes get calls asking me to do a Division 15 or Division 16 only inspections (they may also want Division 26 which was formerly under 16 and perhaps 27 and 28 which were formerly under 13).
If potential clients get my name from someone else and do not know me personally, they may ask if I can handle one or more other divisions. I tell them that I can coordinate all the activities for all Divisions as their Owner’s Rep. It is not uncommon to have a potential new client say something like I have everything covered except xx, xx, xx, and xx but once they know you are experienced as an Owner’s Rep, they may ask you to serve as their Owner’s Rep coordinating the activities of the others who have already been brought into the project. On large inspection projects, I am usually able to give clients a fixed price. If there is more than inspection involved, I quote an hourly rate.
The bottom line is that there is a lot of commercial work out there. It is interesting and profitable work. In some respects, it is easier to do commercial work than residential. The best part is that it is also usually more profitable.