Why thank you 9999 or should it be 666 ?
Not sure where you are getting your numbers from but some of them need to be revised.
Insurance :
We run a 55 ft ketch and have insurance from Pantenieus, full coverage soup to nuts plus a liability coverage to 5 million euro injury or death. Cost per year 3000 euro
Mooring fees :
Not a bad guess but down this neck of the woods a little more expensive 600- 750 a month euro.
Maintenance:
Here is where you come unstuck, given the annual haul out cost and bottom painting for a 55 footer plus parking fee on the hard and may be you may get away with 2000-3000 euro for a 4 month stay out of the water. Really by the time you upgrade things repair stuff and change things your winter maintenance bill can easyily reach 7000+ euro. Do''nt forget the gentleman wants to offer a top notch service and needs all those nice things, linens,plates, toys, etc its all about service and being reliable....
Foriegn flag or national flag...
Never thought about this did you ? Run an english flag charter yacht and you have to under go MCA charter construction requirements. They are VERY VERY TOUGH, things like water tight bulk heads, gunwhales that can not be abouve such a hieght,
pumps must be certain size etc etc. you know who the english love to be over cautious about every thing. Plus do''nt come down to greece and charter with a foriegn flag, you will get arrested or worse get your yacht impounded. Only greek flag yachts can offically charter here in greece, oh we do get a few foriegners trying it on now and again, but they are easyily spotted and then the port police pay a visit, next thing clients and skipper are vacacating greek waters.
You can charter here in greece but first you must set up a greek company and run the yacht though it, thats how you get your greek flag...
9999 did have some good advice, sail and work for some one else first, jumping in to this with no experience will only get you into trouble and loose any money you invest, I know its a dream but its a shark eat novice world out here, and the market place and boat yards are full of well meaning individuals and left over charter yachts...
Good luck in your quest
Sailmaster25