We took the plunge about 3 years ago and invested into a trailer. It was a good option for us since we were showing almost every weekend and paying haul fees. There are pros and cons to owning a trailer, but for us, the benefits outweighed the negatives.
Pros and Cons
Cons -
Maintenance - this is the BIG one! The trailer will always need maintenance to stay safe. Tires, bearings, floors, are just few items that will need to be maintained.
Additional Work - before the horses are loaded and after they are offloaded, you will have more work to do, as far as cleaning, parking, hooking/unhooking. Sometimes, this can be trying after a long trip and all you want to do is go home and sleep.
Pros -
Schedule - you don't have to rely on someones else's schedule. When hauling to shows, you may have to go early or stay later if someone else is hauling to ensure your horse is being cared for on the grounds. If you have your own trailer you can arrive and leave according to your show times. BIG PLUS!!!
Possible Additional Income - at times we will be asked to haul another horse to the show and we will receive a haul fee. For us it really just helps off set show fees, but it adds up throughout the year.
Storage Space - we park our trailer at the barn we ride with. The trailer provides great, secure storage. The trailer's tack/dressing room serves as storage for our chairs, pop up tents, buckets, saddle pads, polo wraps and more. There is only so much room in the tack trucks at the barn, so this allows my daughter to keep most everything at the barn.
Independence - you don't have to rely on someone else to take your horse off the property.
Trailer Shopping Advice
I would have liked to go back 3 years ago and tell my past self a few things that would have helped with the trailer buying experience. We bought our first trailer based on our budget alone, but it didn't have a tack room. That caused more headaches that it was worth, so we ended up selling that trailer and buying one with a tack room.
List out your needs - it can be exciting when starting to trailer shop. You may become overwhelmed with all the options that are out there. However, before you even start to shop, list what you NEED (the non-negotiable) stuff and with this think long term - i.e. Do you plan to purchase a larger horse down the road that you will need a warmblood size trailer, are you planning to do a lot of trail riding and need water storage, does your child have a ridiculous amount of saddle pads, wraps and accessories that will need to be stored in a dressing room? Stick to what you need and do not compromise, because you may regret it and be in the market for another trailer.
Don't get too attached - I have found the perfect trailer online only to be disappointed because it is already sold or didn't look anything like the pictures.
Bring your negotiation skills - one thing i have learned in the horse world is prices are very negotiable. The worst that can happen is the seller says no. However, I would advise against offering $2000 for a trailer listed at $7000, you may not even get a response. Have a method to your offer, for example, I will offer $6000 for a listed $7000, since it needs new tires and a good cleaning. Tires will run about $500-$600 for a 2-axle trailer in my market. And I will tell the seller what I will need to put into it. They may say no, or they may go with the offer.
Take a friend - take someone who knows a bit about trailers to come with you and has no vested interest in your purchase. They can be the neutral party that may be able to point out things that you may over look due to your excitement.
Always check the floors!!!! - no matter wood, aluminum, synthetic material, check the floors to ensure they are in good condition. Rubber mats can hide things, yes - they can be a pain to move, but move them when you look at the trailer.
Ask lots of questions - ensure you come with all of our questions. I would even write them down just to ensure you get your questions answered.
There are many more specifications and details that people will look at during the process, I consult my "trailer expert" when we are shopping for trailers to ensure what we are being told is accurate and we are getting it at a fair price. Just remember this is a process - it may take days or months depending on what is out there. There is a trailer out there that is meant for you!!! Happy Shopping!