I wouldn't to that for business server. These days RDP alone is not secure enough. I would suggest to put VM with RDP in private network (in Azure) and VPN gateway: https://learn.microsoft.com/en-us/azure/vpn-gateway/vpn-gateway-about-vpngateways.
First, you authenticate on VPN (which is harder to break/exploit assuming that you use strong passwords) enter backend network and then do RDP to your business VM.