Or are they going to be seperate URL’s, eg: myshop.com and myrealestate.com?

There’s really two options.

First, you can create a HTML splash page, and do two separate WordPress installations in the sub-folders, and run them independantly. That will give you two seperate sites that don’t rely on each other in any way. You can use separate databases, and everything is kept to itself. The good thing is if something goes wrong with one site, the other site will keep on functioning. The bad part is that the sites won’t share anything at all.

Second, you can create a Network, and have your main site with the splash page, and two extra sites, one for each section. This will let you use different themese and have different settings on each site, but the sites will be run from the saem code-base and database so everything is encapsulated nicely. You can also share users between sites, so someone that registeres for the shp can also use that login on the real estate site. The only downside to doing it this way is that it’s a little more set up work, and you do have to run off a single database, but if it was me, this is the way that I’d go.

Multiple WordPress installations would work well, but a little “extravagant” from someone used to Dreamveawer. I still need to be reborn here.
Creating a Network I think is too ambitious for me now, being a rookie. Is it possible to do the multiple installations first and change to Network later without too much fuss?
Then another stupid question. What is a splash page and how do I create it? If The WordPress manual describes this procedure i guess i should be able to find it my self.
Thanks again for the help

To be honest, trying to change from multiple sites to a netowrk, or from a network to multiple sites, later on is just a pain. Whatever you decide on for a start is what you should stick with. Don’t be too worried about a netwokr being too ambitious. It’s not that much different from a standard site, but if you are concerned, stick with two separate installations.