It's not too difficult. There is a fair bit of bureaucracy, so I would recommend going through a lawyer here. The essential requirements are a fair bit of documentation (birth certificate, marriage certificate if appropriate, and your FBI report) each of which have to be apostilled and submitted within six months of the first documents date. Then once you've submitted all your paperwork you'll go in process, after which you won't need to leave the country every 90 days to renew your visa.
Once you've been approved, if you're going to be in the so-called "rentista" category (i.e. not retired, but not working in Costa Rica) you need to show proof of bringing in at least $2,500/month to the country for 24 months. That can be done by transferring $60,000 into a bank here, which will dole out the $2,500 to you every month, or, in some cases, you can provide a different proof of guaranteed income.
After three years you can apply for permanent residency, which at that point is more a formality, and is pretty automatic unless you end up with a police record or some other issue.
Once you've been approved, if you're going to be in the so-called "rentista" category (i.e. not retired, but not working in Costa Rica) you need to show proof of bringing in at least $2,500/month to the country for 24 months. That can be done by transferring $60,000 into a bank here, which will dole out the $2,500 to you every month, or, in some cases, you can provide a different proof of guaranteed income.
After three years you can apply for permanent residency, which at that point is more a formality, and is pretty automatic unless you end up with a police record or some other issue.