If you have a USA passport, you don't need a visa. When you go through immigration on arrival, your passport will be stamped allowing a stay of 30 days -- no fees. After that, you just keep going to the nearest immigration office every 30 days for new stamps -- these will cost you. After 12 months, you can apply for permanent residency. More details can be easily found by searching.

Although you are required to have an onward/return ticket and sufficient funds, it's unlikely that you'll be asked to show them.