Living on Costa Rica. How far can 5 million colones dollars go?

Five Million Colones is about $10,000 USD right now. That won't get you very far. Also, Colones and Dollars are completely different, you can't combine the two. A lot will depend on how and where you want to live. You can get a small house by the beach for $500 a month, you can get that same small house in the area I live in for $100 a month. It's all about location. If you go to a tourist town or a beach town it is going to cost you. You go to a small town that is more inland and you can live much better. Believe me, there is plenty to do inland and in small towns.

Depends on how you want to live.

That's the equivalent of $10,000 US Dollars.

If you will be spending time near any beach, staying in any establishment that caters to tourists, and eating at restaurants then it will probably only last you about 10 weeks if you are somewhat frugal with your money.

If you are going to be in a more rural area, or a city that does not cater to tourists, renting something longer-term, buying food in a grocery store and cooking at home, it can last several months.