I'm not sure about your dog shelter, but ours will not let you adopt unless your dog has updated shots/vet visits.

Our vet sends out a postcard when we're due for shots. We do them every year.

Each vet check-up normally costs us around $160++ (per dog)but it also may change with the Vets near you.
But, we sometimes buy Heartworm Prevention (which I suggest you do if not already) when we go, depending if we need it or not.

Call your vet and ask.