I would look into hosting your applications/data with a cloud hosting provider. First, I don’t want to come across as trying to sell you something, but I will tell you what I charge one of my customers for a similar solution so you can have something to compare.
This customer needs file storage and QuickBooks. Currently they run their QBs on my hosted environment for $250/month which covers them for 5 users and includes MFA, MS Excel (for reporting) and management. Another option is to go with public cloud, which you could manage yourself or outsource to an MSP. Even a bare metal provider could be a better option than on prem.
For the file storage we are in the process of migrating to Office 365 OneDrive. This limits the local network services to DHCP and internet access. I use pfSense for firewalls and found this type of solution to be the best value for small businesses.