You discuss a number of issues, but don''t mention one which in my opinion is critical - quality construction and systems.
At your budget, you will not be able to get a relatively new, top quality boat with full offshore cruising equipment. With a limited budget and an older boat, I would first look to who makes the boats with the best reputation and then look for those that look to be well maintained. Given your constraints, I doubt you''ll have the luxury of picking from a lot of alternatives.
There''s a HUGH difference in boats that will take you to Florida, to the Caribbean, and to Australia. There are a lot of factors in your decision, but my gut feeling, from someone who has been there, is to buy an inexpensive coastal cruiser with good resale value. Then head to Florida and maybe the Abacos. When you''re ready, sell her and by then you''ll know what the next step should be.