Ask HN: Do you know a good and simple vulnerability scanner?

I tried a few vulnerability scanners like Nessus, OpenVAS, …, but it’s usually too complicated to use if you’re not an expert or it’s very expensive. It would be mainly to scan my servers on the internet. (If possible without installing an agent on the servers.) Do you know an easy-to-use and ‘low cost’ product that I can use to scan my servers on a daily basis ?