It is always good to start saving for a vet fund as hamsters can get sick and can be treated for many things and costs can mount up (I had to pay £40 many years ago to have a hamster pts.. out of hour costs can also be triple or more that). Being registered with a vet also gives you an idea of costs that you may encounter but also if you need an appointment, some vets prioritise those already registered.
It is always preferential to have an exotics or small furries specialist but they are hard to come by. That said, making enquiries and finding the right vet for you is always good to do in advance