For a small business website and client portal, we'd usually focus on reliability, backups, and support just as much as the server specifications.
Your requirements of 4GB RAM, NVMe storage, and a budget of around $20/month are quite common, so you should have several options within that budget. Beyond the hardware, we'd also pay attention to uptime history, backup policies, network quality, and how responsive the support team is when something goes wrong.
When working with business websites, we've found that reliable backups and responsive support are often just as important as CPU or RAM specifications.
Before choosing a provider, it's worth comparing what's included with each VPS plan rather than looking at the specifications alone. Small differences in support quality and reliability tend to matter more over the long run.