local ports collection

[till plewe]

I would like to use the ports tree to install and manage packages inside my
home directory. I tried setting:

PKG_DBDIR,PREFIX,PORTSDIR,LOCALBASE,PORT_DBDIR,DESTDIR

to directories within my home directory but then I get error messages like

$ make build
===>  Creating some important subdirectories
mount_nullfs: Operation not permitted

when trying to build/install ports.

Any suggestions on how to use ports completely avoiding root?
(I rented space on a server and have permission to install binaries
but do not have root access)

Thanks.

- Till

PS I used portsnap to get the ports tree and the server is running FreeBSD 9.1)