Does your home office router or hardware firewall - if you have one offer a built-in VPN server? If so it might do the job. If your just using the standard home broadband router issued by your ISP it is unlikely to offer such a feature. (You could potentially replace it with your own.)
I have setup StrongSwan5 in a Linux VM running on a Mac. StrongSwan5 can provide both Cisco IPSec and IKEv2 compatible VPN services, it can also utilise SSL certificates instead of a pre-shared-key. Using certificates is considered more secure than a PSK.
Note: Both the Cisco IPSec and IKEv2 options will work with the built-in Apple VPN client.
I have also setup a L2TP VPN server using the built-in function in a SonicWALL firewall, this then works with the built-in Apple VPN client. The other VPN options provided by the SonicWALL require using either the SonicWALL VPN client or a suitable third-party client and these typically incur additional license fees as well as installing additional software.
As others have mentioned using Apple's own Server.app and its L2TP VPN server is an option. Personally I find this less and less reliable.
Some people chose to pay for a VPN service, this accomplishes the goal of encrypting your traffic via a VPN so someone else say in the same StarBucks could not easily eavesdrop on your traffic but a lot of people have concerns about the trustworthiness of such providers. Even if they themselves are ok if your goal is end-to-end protection they do not cover accessing your home office network, for that you need your own solution.