It all depends on what sort of vehicle you have and if you want to just do UK or if you are thinking of international.
if you have a vehicle which is over 3.5 ton there are a lot more costs involved so when I was looking at it, it only made sense to do either a 3.5 or a large HGV that could take a lot of horses.
you would need the full WATO licence and the driver competency test, an operators licence, a transport manager (has to be qualified) to deal with the TACO etc. If you are going abread you will need more then one driver. the drivers must do s certern amount of driver training every year. You have to have a yard to work out of, the vehicle has to be inspected my DEFRA. You will need the SVS licence. The vehicle has to be serviced every 6 weeks. Drivers and grooms have to have the competency test (different to the one above)
its a very competative industry, working on low margins. so as long as you are happy to be on the road a lot of the time its fine
Sign up for www.horsetransportnetwork.com which will delivery approx 120 new business leads for horse transporting per month. do check out our website for more details and good luck. It's hard work but rewarding