Carol,
I'm not sure I understand. A visitor to St. Maarten could either buy or rent an apartment, and could compare the monthly cost of these two options. In both cases, ownership or rental, if you assume that the rent or annual ownership was continuous, it doesn't matter whether you stay in St. Maarten for 1 night or 365 nights. We're comparing annual costs of these two approaches.

On the other hand, if you choose rental, there are options for seasonal rentals or AirBnB rentals by the month or the week -- and these rental options obviously cost less on an annual basis than owning, assuming one chooses to rent for fewer than 12 months.