In order to have access from internet you need routable internet IPs for your internal or DMZ network. However that means your network would be exposed + the cost of IPs.
😯 what are you talking about??
By the way, VPN is clearly not the solution to this problem…
Rout-able IPs meens IPs that are not in private range. https://en.wikipedia.org/wiki/Private_network. Also these IPs needs to be routed to your place so in most cases you will need to buy them from your ISP for an additional cost. You may need advance networking and routing experience if you will go multiple ISPs.
You didn’t specify if your clients are public or private, most corporations use VPN to allow their employees to access internal resources.
I suggest that you should stick with forwarded ports.