Hi Eryc,
As one who has embarked on the Private / Charter aspect of boating - I believe that you are probably going to be disappointed if charter income is in your sights with the type of boat you envisage.
We have just gone through the process "certification" of our boat for Charter (she is a Dufour Nautitech 475) and it was no easy feat - and very expensive (Over $US 45,000.00 in additions / modifications)
Our boat already had DNV Classes 1, 2 & 3 certification which is a pre-requisite for ANY type of charter operation, anywhere in the world these days. However, this was not good enough for our authorities (Australia), and we had to complete some re-wiring, add bilge / firefighting pump (1,100 ltr / min & 220v at that), watertight bulkheads & additional floatation. All the relevant safety gear - it all adds up.
It is true that in some areas - and I travel extensively throughout SE Asia - that you could get away with using your boat - after all, foreign currency in developing countries can buy anything.
However, have an accident with no insurance (our Charter Insurance runs to $A 8,000.00 pa) in some of these countries and "Midnight Express" would be a picnic in the park compared with the trouble you could face - and NO embassy will get you out of it !! You must remember that life in these areas is very cheap, and although your lifestyle is a modest one in the Western World - the areas you are planning to go to make you a very wealthy fellow in their eyes, and a target to milk at any opportunity.
Cruisers to these areas may well disagree - but they are not planning to establish a business and are not dealing with locals in business on a daily basis. It is a very different side when you start to mess in marketplaces of the local population. It is also fair to say that some cruisers have established charter operations in SE Asia - but there are not many, and the boats tend to be in the 60'' and above range and of a quality that attracts clientele year after year.
I am not sure of the market you are chasing - but you would need to conduct a fairly carefull evaluation of the boat, its load carrying capacity and its ability to be certified. Once you know your market - then you can look to the boat that best suits your purposes. Perhaps in your situation looking to the ferrying of say "Back packers" could be worthwhile ??
My experience in business (Oil Industry) in these areas extends to Indonesia, Malaysia, Phillippines, Brunei, Myanmar, Thailand and Pakistan, and spans 25 years in these areas. I have already researched the options of sailing these areas and offering our boat into the local charter markets, and to this end, we won''t be bothering !! There is just too much beaucracy to battle, import regulations, residency problems, taxation issues etc etc. and everyone "wants a piece of your ass" !!
Other people have commented about the necessity of having a local agent - you need it - but the biggest single problem is finding someone you can work with, will produce results, and won''t steal from you. This process actually took us 5 years in Indonesia - and we are a multi-national company with fairly healthy resources to fall back on.
My personal opinion, is that you should get the boat within your means, travel / sail to the country and then look to your options. Quite frankly, you would probably be better off supplementing your income by offering services within your own area of expertise. The income from Charter ops is extremely spasmodic and takes many years to build up a clientele.
We even looked to linking up with hotels in these areas, but in order to elicit any interest - you need to have a "showboat" with all the "bells & whistles".
I do apologise for being a little negative here - but please be aware that the sort of operation you are contemplating is fraught with danger.
Like yourself, we have had similar goals - but after spending a good deal of my time in these areas - the dream is vastly different to the reality.
If you want some further insight - please do not hesitate to contact us, and I can go into greater detail - because we have researched it all !!
Cheers
Rodger