Payment for health insurance will be made after approval i.e. Stage 1 has been granted.
The cost of basic health insurance is £624 for each year. So if you are requesting a visa for 5 years, multiply that amount by 5. And yes, you have that option to request a visa from 1 to 5 years🙂 .
If you are planning to get UK citizenship, then specify a maximum of 5 years.