I suggest you DatingPro (http://www.datingpro.com/) and Dolphin (http://www.boonex.com/).
Other valuable dating scripts are:
http://www.datingscripts.org/
http://www.abk-soft.com/
Ok, first off, none of those are... GREAT. they all have their flaws,
2nd, for the guy that said stay away from ABK,
its a good peice of software if you know what your doing.
i bought it and love it.. a few things i didn't like but, if you know php at all, you
can fix it.
don't get any of these, buy Social Engine, you will have to intergrate a few things in it. like with any script.
and plugins cost extra, but its the most user friendly that is out there.
other than that, why not just build one off of boonex or joomla.
if you know a good php coder, have them JV with you and split the cost. and split the income, but only if you can make it turn over some income