It is very common for a webserver to only have 1 IP address. IPv4 addresses are getting scarce, and people don't want to use more than they need.
From a security point of view, it makes it slightly easier for an attacker to find other services on that machine, but it makes little difference. A seperate network card on a different network for management can be a security measure, but just a second IP address on the same network and interface isn't.
In any case, you want to make sure you have properly configured your firewall, as well as secured services like remote desktop - if remote desktop is opened to the internet at large, it will get hammered with attacks, and some may eventually succeed.
One reason you might want to have multiple IP addresses is if you are running multiple HTTPS sites, since it is much easier to setup and better supported if they are using separate IP addresses, not name based hosting.