This is what I pulled off qhorses.com:
Do You Need A DOT Number?
The laden weight of your truck and trailer is important as you may fall into the category of needing a U. S. or state D.O.T. (Department of Transportation) number or CDL (commercial drivers license).
Do you need a DOT Number, logbook or Commercial Drivers License if you don’t haul horses for money?
If your vehicle or combination of vehicles has a GVWR (Gross Vehicle Weight Rating) or GCVWR (Gross Combined Vehicle Weight Rating) of less than 10,001 lbs., you do not need to be concerned about these things. However, if your rig has a GVWR or GCVWR of 10,001 lbs. or more, you must make some decisions. (The GVWR is determined by the manufacturer and should be marked on your trailer and your tow vehicle. The GCVWR can be obtained by adding the two together. A two-horse trailer and a pickup truck can easily be rated over 10,001 lbs.).
Even if you don't haul horses for money, the US Department of Transportation (USDOT) can consider you "commercial". Operating a commercial stable, hauling horses for show (with intent to profit), rodeo, race, sale, training, or for compensation are examples of "commercial ventures" as defined by the DOT for those who are traveling interstate. Those who only travel intrastate need only be concerned with the regulations within their own state of residence. Most states have the same regulations and some have even more stringent laws.
If you fall into the commercial category, you must follow the Federal Motor Carrier Safety Regulations (FMCSR). This means that you must carry a logbook, medical card, certain safety equipment (such as flares, triangles, fire extinguisher etc.) and your vehicle must be equipped with certain features such as required lights, safety chains, brakes, and breakaway brake. You must also have a federal inspection sticker, ID number, and a sign on your truck.
For interstate travel, a commercial drivers license is only necessary for driving a vehicle or combination of vehicles over 26,001 lbs. Some states have additional classified licenses for those who drive vehicles or combinations under 26.001 lbs.
Farm exemptions are available, but if you have a farm plate, you may not travel more than 100 miles from your farm.
Explanation of GVW, GVWR, GCVWR, and GW (weight terms for your truck and trailer)
GVW (Gross Vehicle Weight) and GW (Gross Weight) are interchangeable terms meaning the actual weight of the vehicle (trailer) and its complete load. This weight can be determined by loading the horses, tack, feed, and hay etc. into the fully equipped trailer (mats, spare tire, etc.) and taking it to a truck scale to have it weighed. Most gravel yards or truck stops have truck scales.
GVWR (Gross Vehicle Weigh Rating) is the value specified by the manufacturer as the recommended maximum loaded weight of a single vehicle. For a trailer this value is determined by the axle capacity and the coupler capacity. For example, a trailer will be rated at 5000 lbs. GVWR by the manufacturer if it has two 2500 lb. axles and a 2 inch ball coupler that is rated 5000 lbs. Loading the trailer to excess of the GVWR is not only unsafe, but is illegal.
GCVWR (Gross Combined Vehicle Weight Rating) is the value specified by the manufacturer as the recommended maximum loaded weight of a combination of vehicles. (The GVWR of the tow vehicle plus the GVWR of the trailer.) In the absence of a value specified by the manufacturer, GCVWR will be determined by adding the GVWR of the power unit and the total weight of the towed unit and any load thereon.
If your vehicle or combination of vehicles has a GVWR (Gross Vehicle Weight Rating) or GCVWR (Gross Combined Vehicle Weight Rating) of less than 10,001 lbs., you do not need to be concerned about these things. However, if your rig has a GVWR or GCVWR of 10,001 lbs. or more, you must make some decisions. (The GVWR is determined by the manufacturer and should be marked on your trailer and your tow vehicle. The GCVWR can be obtained by adding the two together. A two-horse trailer and a pickup truck can easily be rated over 10,001 lbs.).
Even if you don't haul horses for money, the US Department of Transportation (USDOT) can consider you "commercial". Operating a commercial stable, hauling horses for show (with intent to profit), rodeo, race, sale, training, or for compensation are examples of "commercial ventures" as defined by the DOT for those who are traveling interstate. Those who only travel intrastate need only be concerned with the regulations within their own state of residence. Most states have the same regulations and some have even more stringent laws.
If you fall into the commercial category, you must follow the Federal Motor Carrier Safety Regulations (FMCSR). This means that you must carry a logbook, medical card, certain safety equipment (such as flares, triangles, fire extinguisher etc.) and your vehicle must be equipped with certain features such as required lights, safety chains, brakes, and breakaway brake. You must also have a federal inspection sticker, ID number, and a sign on your truck.
For interstate travel, a commercial drivers license is only necessary for driving a vehicle or combination of vehicles over 26,001 lbs. Some states have additional classified licenses for those who drive vehicles or combinations under 26.001 lbs.
Farm exemptions are available, but if you have a farm plate, you may not travel more than 100 miles from your farm.
Each state has a different weigh station policy. All commercial vehicles must stop, but sometimes even non-commercial vehicles must pull in. As a general rule, if the sign says "All Trucks" must pull in, it probably means pickup trucks too. Some states want to see vehicles that have "commercial" plates even if they are not classified "commercial" by use. They may want to check vehicle registration, driver's license, weight, or safety equipment and often they will want to see the health papers of the horses or do a brand inspection. Most of the time, the weigh station personnel will be too busy with big trucks to bother with you and they will probably wave you on. Some people have even been told they should not have stopped. Horse trailers fall into the cracks, and any enforcement official has the option to enforce the regulations as he sees fit. Any sign that says "Vehicles with Trailers" or with "Livestock" means you must pull in. In this case, they will want to inspect the horses. If you do not stop, they may pursue you and bring you back. The fines can be very steep and you can be held for a very inconvenient period of time.
What I am getting out of this is that even though our combined weight exceeds 10,001 lbs, as long as we are not considered commercial we do not have to have a DOT# even if traveling through a DOT state. We are just going to pick up a horse we purchased. Now, if we were going to go to a show, we could then be considered commercial. Am I reading that right?