Hello guys,

tonight I had the same issue and with some hints from the #n900 channel I was able to arrive at a quick fix to do what we want it to do... but it's that..a quick hack. Next time you update your packages it will be written over.
Apparently the N900 does not use the SysV init files that we all know and love but it uses upstart

so, to solve our little problem, I simply changed the file responsible for starting ssh

go to /etc/event.d and edit sshd with your favorite UNIX aware text editor.

replace:
with

By commenting it out it won't be started automatically.

That's it. Reboot your phone and all is good.