Ask your trainer where her clients board. Call those places. When you get all the details/visit, make sure you ask what farriers/vets they use. Even if the barn is fine with you bringing in whatever professionals you want, that may not be feasible for you if you can’t be there for the appointments. It can limit your ability to ‘bargain shop’ in a way that you don’t always realize going in.
When I boarded in Maine the facility had a beautiful indoor arena. Board was $450 with a run in shed. Higher if I wanted a stall. It included grain and hay. I had to provide supplements. Here are other fees I paid:
farrier: $45 every 6/8 weeks (barefoot trim)
dentist: $100 1-2 times a year
annual shots: $200+
trainer: $45/hr
tack: (varies, saddle, halter, bridle, blankets, bit, etc) $1,000+
emergency vet bills: they DO happen $500+