As well as the actual property, what can I expect to spend money on?
Typically there are no legal costs or stamp duty when buying a park home, but you may want to utilise a solicitor. If the home is a second hand home you should consider a structural surveys that you may require  by a specialist park home surveyor and any necessary decorating expenses.

What is the best mortgage I could get?
It is not possible to obtain a mortgage on a Park Home, as mortgages are secured on land, but when you purchase a park home you do not buy the land. However specialist lenders such as Park Home Assist are able to provide specialist financing packages just like mortgages to assist in your purchase. Broadly speaking there are 2 different options; repayment and interest only. Unlike mortgages the interest rate is fixed for the entire term, so you need not worry that interest rates will increase and make your finance unaffordable.

Is it okay if I take pictures on a viewing?
This is actually a very good idea, and should not be a problem, but for the sake of etiquette ask the seller's permission before snapping away.

How important is it to know the state of the property market?
This information could prove very useful. For example, if it is a buyers market you could get away with offering less for the property than you first anticipated.

Do I have to pay stamp duty?
No. There is no stamp duty on park homes.

Should I get surveys done on the property?
If you have any suspicions about a property you are interested in, or if you just want some peace of mind before purchase, then a survey is a good idea.