If you have a licence look at the 6-7.5t ones, far better value. I hate to say it but you look far too young to have 'grandfather rights'!!
We have had Ivecos, Mercedes and Dafs and every thing from 4.5t to 7.5 t, about to have our 7.5 t upgraded to 8 or 10 ton.
What ever you choose, ask for and check the weigh bridge certificate. If you can then ask to load up your horses. tack, partners, helpers , water, fuel etc and weigh again. These days you may well be pulled off the road for weighing, failing may mean you are stranded and have a very large fine, not worth the risk
I hate to say but I do not know of any safe 3.5t that takes two horses and very few 7.5 with living ...the best manufacturers now say two horse max on a 7.5t with minimal living, ours will only carry one skinny TB legally,hence our uprating it. However uprating introduces a whole new world of tachos and permitted hours!!