Here are a few things which should be kept in mind to make the right decision.
Weight Class Of The Trailer
It is crucial to decide the right weight class of trailer depending upon the kind of car you want to transport. Think carefully about how many cars you want to transform through car trailer to decide the accurate weight class of trailer.
Capacity
Trailers are made to transport either one or more cars. If you plan to transport more than one car in the near future, it is advisable to go with a trailer which can house the desired number of cars. Proper analysis of the capacity of the trailer will also help you to decide about the number of axles you would need in a trailer.
Apart from that do proper research about the prices and buy a trailer with complete paperwork to avoid any legal hassle.