You can use the vpn service of your server easily but you need a vpn service on your end as well either software or hardware their should be some free software if you would like to do it free for security reasons hardware is better you should check to see if your router is already VPN capable lots are.
Pc Anyware will work but you need someone on the other end to accept you each time.
Using Dnydns and remote desktop without a vpn will work fine for free
The vpn will give you security on transmitted data and make it as if you are at work so you can print from your machien to a work printer or access the file server all as if you were at work.
Most companies require a VPN for security reasons but it is not an obligation just a strong recommendation.