what experience do I have to have??
The Charter Companies are looking for a valid credit card. That is 90% of your qualification to charter. The sailing resume you fill out accounts for an additional 5%. Some may disagree but I challenge them to prove it. The manner in which you and your party conduct themselves upon arrival fill in the rest, however that last 5% can also be a killer. Being polite is always best. I bet, some local fellow will judge you worthy down there after he has seen you.
Study before you go. Be honest about your experience. You have plenty. Be very careful and watch out for the other charter boats aroung you. Some get by with no experience at all.