From the perspective of employment pension security, people who engage in paid employment are either employees or entrepreneurs. In either case, pension insurance is required with certain conditions in order for you to accumulate a pension.
On the basis of the information you have provided, YEL insurance (pension insurance for the self-employed) would likely be the best option. This means that you will have to purchase a YEL policy yourself. The Tyoelake.fi service contains information on when you need a YEL insurance policy- An entrepreneur’s pension contributions and pension and sick allowance are determined by your income, which you and your insurance provider have con-firmed.  If you invoice your customers via a service enterprise, you must also purchase a YEL policy.
If you have not had YEL insurance previously, you will get a 22% discount on contributions for the first four years and contributions are tax deductible in their entirety.
You can also carry out the work you have described and earn an income as an employee. In this case, it must be clear whether the customer commissioning the work is an employer or is commissioning work from an entrepreneur.  An employer pays a salary, pension contributions and other social security contributions. For example, the employer withholds the employee's pension contributions from the employee's salary and pays these to the insurance provider with the employer’s contributions.
Both parties (the party carrying out the work and the party commissioning the work) must be certain before work begins, how the work will be paid for. For this reason, it is advisable to draft a written employment contract or commission agreement even for short-term work.
The Tyoelake.fi service contains information on the characteristic features of employment and entrepreneurship. Pension insurance companies also provide advice. Make sure, you have these matters sorted well in advance. This will ensure that your security is provided and do not need to pay unnecessary fees for late payment.