What do you think (just a estimate) will be a realistic figure in dollars to have per month. My boat is paid for and I have no other debts. Actually my biggest concern is the mooring fees at different ports
There is some discussion about this on the Cruiser Log
sailing forum. http://www.cruiserlog.com/forums/forum.asp?FORUM_ID=2
, and I've tried to answer this question several times.
Here's my revised take on cruising costs.
In a nutshell. Figure out how much you spend for living now. Deduct those expenses associated with land living - rent and/or mortgage, taxes, heat, electricity, telephone, television, etc. Add 25% to your food costs (that's a high estimate, I know, and you will rarely look at that, but it's a good base line), budget $2,000 or 2% of your boat's replacement value (whichever is higher) for maintenance and repairs - and make sure you have that cash available all the time. Maybe $100 a month or so for ancillary expenses - mail, internet access, buses and taxis, etc.
If you enjoy sailing, fuel costs should be pretty low. The amount of power-hungry gear will determine whether you need a generator or will run your engine frequently to charge your batteries.
Food costs will probably be higher, though it depends on where you will be sailing. The Caribbean and the South Pacific islands are quite expensive because most food is imported. Beer, wine, and liquor seem to me to be the biggest budget busters. Non-drinkers live much more cheaply than drinkers.
Maintenance and repair parts for your boat will be higher, up to 50% higher in some places - again because most of the places to visit in the tropics do not have a local industry in what you are seeking to buy.
On the less expensive areas.
There are very few places that we encountered where it cost anything to check in (pennies, not dollars). Few isolated places where the locals would charge you for anchoring your boat (and we just left). I think that Australia was the most expensive country to obtain a visa for (though I understand that the US now charges for a visa for people visiting on a yacht). You can check further on that aspect at Jimmy Cornell's Noonsite web site.
In general, the average cruiser in the tropics no longer has expenses for heat and electricity. No property taxes. No expenses for Television, or telephone. Various services for email access can impose a monthly fee to the cruiser, though a barebones cruiser can rely on "snail mail" and visits to internet cafes when in port. 10 years ago the Internet wasn't such a pervasive presence in our lives, and cruisers survived without instant communication. 24/7 access to the Internet is nice, but not necessary. That will reduce costs.
Your own standard of living, and what you feel is a minimum level of comfort, is the best indicator of what your cruising costs will be. We lived pretty cheaply because we didn't like marinas very much and preferred anchoring out, we mostly visited underdeveloped nations rather than the expensive, consumer-oriented First World countries, and though we did a lot of land exploring, it was usually done the cheapest way - via buses and trains and feet.