Visa renewal process

We plan on moving to CR before year end. Since it will still be wintery conditions where we plan to come back to visit in the U.S., our plan is to make a border run after the first 90 days , then make a U.S. visit after the next 90 days. At that point, we will decide if we want to pursue residency and can start paperwork on our visit back.

My question(s): Can we fly in on RT  tickets - how do we prove to immigration/customs that we will exit at 90 days? Do we make arrangements prior to show proof (how to do this?). The Rt return date would be 6 months out.

You may or may not be asked for a return ticket to your country of origin.  We have never been asked but many I know have.  Please keep in mind that you do not automatically get 90 days stamped in your passport.  One trip we got 14 days.  It is totally up to the discretion of the immigration officer.

When you check in for your departure at your home airport, you may either have to change the date to within the 90 days timeline, as required by Costa Rica immigration policies or once you land in Costa Rica at the immigration desk.

It all depends on the customs person you encounter, some will ask to see your return ticket within the 90 day period, and others will not, it's a game of luck.  One guy didn't have a return ticket so they sent him over to the airlines counter to buy his return ticket before they allowed him into Costa Rica.  You could have a prepaid bus ticket showing you are going to say Panama, as if you were going to visit Panama before going back to your country.

It has nothing to do with customs Edward.