Install DHCP: Install net/isc-dhcp3-server you can use this config file dhcpd.conf, stick it in /usr/local/etc/.
Enable tftp:
Make a directory /usr/tftpboot
Add this line to your /etc/inetd.conf:
tftp dgram udp wait nobody /usr/libexec/tftpd tftpd /usr/tftpboot
Enable NFS:
Add this to /etc/rc.conf:
nfs_server_enable="YES"
Add this to /etc/exports:
/usr -alldirs -ro
Reboot to enable the new services or start them manually.