How to become ISO/IEC 17025 certified and cost associated

I do not know who can and how much it is to become certified 

Please note that the correct term is accredited, not certified; as it involves formal recognition of competence.

The process involves implementation of ISO/IEC 17025:2017 by establishing systems, processes and documentation; followed by evidence of implementation and maintenance in order to apply for accreditation.

Accreditation involves contacting your national accreditation body or selecting one if you have a choice; application and then a competency assessment. The costs will depend on the accreditation body. You will need to request a quotation. In awarding accreditation, the accreditation body attests to your laboratory’s competence to provide consistently valid results through meet the requirements of 17025. An accreditation certificate, which details your scope of accreditation is then issued.

how often we will need to be re-certified.

There is an accreditation cycle of 4 to 5 years, with a number of followup assessments. The first is 6 to 12 months after initial accreditation is awarded. At the end of the cycle, a full re-assessment is made again (as if you were applying for the first time).

Have a look at our free webinar on demand - What are the steps in the ISO 17025 accreditation process? It includes explanation of the application process, and the accreditation cycle, and is available at https://advisera.com/17025academy/webinar/what-are-the-steps-in-the-iso-17025-accreditation-process-free-webinar-on-demand/