It should be inspected again before the sheet rock is put on. This part of the inspection looks at framing, fastening schedule, flashings, roofing, windows, electrical, plumbing & gas utilities, insulation verification, and a/c duct work.
Finally, the house should be inspected again when all the construction is complete.
However, it's important to understand that inspectors are not omnipotent and have no liability for their opinions. The most important thing is to research the builder, their standards and procedures, and their reputation in the community. Ask questions that you have along the way - you should expect prompt answers from the builder's representative.
If you do have problems in the future, neither the real estate agent or the inspector can stand behind the home - the builder does.
Buying a home is a huge investment and care should be take to protect your interests. It's my opinion that the owner should be following the construction of their home closely and documenting its progress with pictures from beginning to completion.
The builder will take the position of it not being necessary to have a professional inspection done because it's an additional expense and they will always point out that you have a full (x number) months warranty and a (x number of years) manufacturers structural warranty.
We have been involved with many new constructions that the owners have used the services of a home inspector and it goes without saying, they always find something. Many times the issues detected are major: mold in the attic, missing roof tile, incomplete wiring, etc. Some are often items that the common owner wouldn't find in a lifetime.
Simple stated, todays homes built by builders are only monitored by the developer, with the work being subed out to the various trades people. So there will be different work groups coming in for site work, carpentry, plumbing, electrical, HVAC etc. The trades often get workers that are on the job for only a day or two and they sometimes do not possess the basic skills and are being trained on the job site... Often basically unsupervised.
Today's system lends itself to mistakes being not only made, but being over looked. My recommendation is to plan on doing regular personal inspections along the way in your building process and in the end, have a professional structural inspection as well.
I have seen many houses go on the re-sale market that had items show up in the inspection report that should not have been there.
Builders try to get it right but things get missed, having an extra set of eyes look at it helps everyone.
You should also have a Realtor to work with you on the buying process, most think they don't need a Realtor because they have the sales person to help them. Remember that sales person in most cases is not a Realtor they are an employee of the Builder and so they have not duty to you!! A Realtor can run comps for the area and help negotiate the price as well as upgrades. Their loyalty is to you not the builder. Most builders factor in a commission for Realtors and even encourage Realtors to bring them buyers but that money is not passed on to the buyer if they are not represented. You have nothing to loose and everything to gain by being represented.