I would say then that you'd probably want to have us hand off the site already completed, other than your own content and admin panel/UI related stuff.
Then your only ongoing responsibilities
DIY requirements that fall back onto you.
New Content would be added to the site by you and you can use any of the included shortcode templates to do that and or modify them to create new ones. (videos) Anytime the RETS provider sends you an email about changes to old RETS fields or adding new fields or switching to a new/different RETS provider, then you would need to login and tweak as needed yourself via our videos/forums or hire us/someone to tweak as needed. Listing images are the same as the RETS data - they may need to be re-sourced - again with videos/forums etc. Both of the above can sometimes trigger hosting tweaks needed to the php.ini and or my.cnf and or TCP (ports). (most hosting co. accommodate or have how-to's)
There are other things that can occur, but for the most part, you can typically go without any tech stuff needed more than once or twice over a 2-3+ year period.
I would highly recommend that you run at least 2 sites though (one can be a free.subdomain) so that you can always have a developers version of your live site that you keep in maintenance mode and not allowing it to get crawled/indexed (you don't want duplicate content SEO issues). Then with this second site is where you do all of your trash-testing and learning how to do all the above DIY stuff.
When you're ready for more info give us a call or via Skype = RETS PRO Cheers -