The major difference I can tell among them is how many photos you can load into MLS (from as little as 4 photos to as many as 32).A selection of the sites are as follows.  

My impression (as an inexperienced investor spending a boat load of time looking at MLS results and listings) is that the frenzy for buying properties has been driving up sales prices (folks paying well over asking costs in some cases) and possibly inflating asking prices as well.

Ok, here's a really loaded question with lots of possible answers. 

@Chris May  sounds like the Dot.com bubble burst of 2000.... minor shock wave then make new highs... people at the start ups are probably not fueling the resi market in SF bay area to any great extent.. they will when they go public  LOLMy daughter is a controller at Intel.. what Intel did was willow out the chaff. they let the bottom 10% of their work force go and a lot of retirement  good thing for the company.. they had a lot of dead weight..

But investing in a solid document could pay for its weight in gold.

Our agent expects an experienced contractor or investor with loads of cash to make a low-ball offer on this house. 

The podcasts are worth their weight in gold.

There also was no common area in the house so I decided to remove a bedroom, restructure a load bearing wall and add a new beam.

I am a real estate agent in South Florida and work with loads of investors on the agent side.  

Engineers are typically required when something is structural. 99.99% of rehabs don't involve structural changes, but if yours does such as opening up a kitchen by removing a load bearing wall, or adding an addition or moving beams, putting in a window that wasn't there, then you'll need one.