I believe you need a permit for any type of business, if you are heading to the west of the island, a nice set of sunset wedding shots may be great. Yes some people celebrate their weddings at the beach, best wen done during the week instead of weekend as there are less people at the beach. Some restaurants by the beach may have a hall for rental, then walk to the beach, or even better have the couple arrive to the beach in horses preferably "Paso Fino" while you are taking pictures, maybe even the husband chasing the course with his bride riding away. all in the late afternoon light with the sun sinking in the horizon.
One warning ..... Expect 3 to 6 months for your permit, nothing moves fast in the island.
PS Google "Paso Fino".
I think I made a boo-boo here, you said rental, I was thinking the whole thing, planning, arrangements and photography, sorry.
If only rental, it will depend on your clientele, not too many local people with money in the island, so less income if mostly locals as your prices need meet the economy and people are more frugal.