Well real estate is a great place for workaholics

I am from the US and have been in Costa Rica for 12 years. I blame my wife for keeping me here, she is Costa Rican and we met here. She says she only invited me to stay with her for a while so I could get settled and I still haven't left
As to residency, most of our clients qualify either as pensionados, rentistas or inversionistas. See some details here:
Costa Rica Residency StatusBut you can also work here under a work permit. This is filed through a letter to immigration on your behalf by an employer. You can get hired from the U.S. and your employer will make the arrangements.
A wide open field now is in the customer service centers that many companies are setting up. Costa Rica's time zone, educated population and hard working employees have made it a hot bed for call centers. The people hired locally make good money for Costa Rica and I am confident that anyone hired from the US as a native speaker for improving customer service or supervising would make US type pay. Or at least a higher level of pay than the Costa Rican staff. Fujitsu, HP, Alienware, and IBM are some name companies that have set up new service centers here recently.