What to bring
You would need to bring your own snorkel gear, some wet weather gear of sort, LED torch, personal hygene kit, first-aid kit, Water-proof zip lock bags for your valuables, sleeping bag, sewing kit, warm clothing etc. (it gets surprisingly cold while on watch at night, even in the tropics)
Above all bring practical gear.
Notes:
Bare foot and back-packs are the norm.
Do not forget shampoo that lathers in salt water; in general the cheapest shampoo will do a pretty reasonable job.
Soap bars are of no use in salt water.
Bed linen, some snorkeling and fishing gear are on board.
As far as costs go, so far we have been averaging a bit less that US$160 a week per person.
So I'd count on US$160 a week just to be on the safe side, with the costs.
That includes all food and any diesel we use for the boat.
Customs charges are split among all on board.
I'm conservative with the motor, preferring to sail as much as possible.
If you need medication, bring sufficient for at least twice the time you plan to spend on board........
In remote areas, there is no corner-store.
The following depends on our cruising area:
You are responsible for stuff like: tetanus/yellow fever injections (If in doubt consult you medical practitioner) malaria tablets, anti sceptics, paracetamol, vitamin/iron tablets, etc.
The boat carries a comprehensive medical kit, but you will be asked to replace what you use.
And:
SMILE.

Because your life is about to change.......
+++++Remember, there's no corner store+++++