The first step, as in almost any country, is to become a resident. Once that is established the road to becoming a Citizen is much easier even though it will be blocked at times by bureaucrats. There are some fine lawyers who specialize in helping with these things and I will be happy to recommend some.

The basic information about Residency is as follows.
Any foreigner included in the following categories qualifies for permanent resident status:

FAMILY TIES WITH A COSTA RICAN CITIZEN: Parents, spouses, sons, daughters, and siblings of a Costa Rican.

PENSIONADO: Anyone who receives at least a monthly income of $600 from retirement benefits.

RENTISTA: People with a minimum monthly income of $1000.

INVERSIONISTA: People with investments of at least $200,000.00 in the country or $50,000.00 in specific areas defined by the Government of the Republic of Costa Rica.