Hello @Adel Welcome to Microsoft Q&A community forum!
Thank you for choosing Microsoft Azure. I learnt from the details you shared in the post that you are an accounting firm with 8 employees using accounting software and planning to move the software to Azure.
Before I suggest the possible for your requirement I would like to know, Is the accounting software installed on a machine and that machine is accessed by 8 employees to use the software?
Scenario #1 - If it is just a software installed on a machine, then you don't have move the machine to Azure. Instead, you can host a VM in Azure and install the software on that VM and grant access to 8 employees by assigning them RBAC roles.
Scenario #2 - If it is a server where the software is installed and you want to move completely from on-premise to Azure, you can leverage Azure Migrate - https://learn.microsoft.com/en-us/azure/site-recovery/migrate-tutorial-on-premises-azure?msclkid=a63c5048cf9511ec9f953f82afd7869e
Scenario #3 - If you are planning to set up business continuity disaster recovery (BCDR), then the best option would be to use Azure Site Recovery - https://learn.microsoft.com/en-us/azure/site-recovery/site-recovery-overview
For optimizing cost on Azure, you can refer to the guide here - https://learn.microsoft.com/en-us/azure/cost-management-billing/costs/cost-mgt-best-practices
Hope this helps. Happy to assist further!