A robust PKI implementation.

Pfsense for a free firewall/vpn. Have 3 ports on it (WAN,LAN,VPN Network). Buy a cheap (1gb link speed) switch to facilitate multiple computers, and plug the remote access computers to the vpn network.

This keeps them off of your internal home network from a threat perspective. And can be had for about $100-250 for the setup. Beyond that, you can proceed with whatever design you want, and leverage RDP access.

Many others have better solutions, but this is another way to go about it.