Question: I am just getting started with adobe illustrator CS5 bulding logos. I often see people presenting it as mockups on walls, business cards or more than one logo which can be navigated through. 

How do it do that using Adobe illustrator or I need Photoshop ?

Regards
Vishy

Answer: 
They have pre made photoshop templates to create these super realistic mockups you see. Some you have to purchase but many are available for free. You will need both photoshop and illustrator. 

A great resource is www.graphicburger.com

These are a great idea because it gives the client an idea of what the final product will look like, and it really helps sell certain ideas.
its great that you are starting to use adobe Illustrator! 

for creating logos, you are already on the right track. If you want to use your logos to create business cards or mockup designs using your logos, it is best using Photoshop if you have it.

You can first save you logo from illustrator either in an eps or pdf format and transfer it to Photoshop. the beauty of it is that your eps file will adapt to any size in Photoshop depending on the size of your file. 

sample:
![eps file placed in a 1920px, 1080px blank doc in photoshop](https://i.stack.imgur.com/E0tuC.png)
![eps file placed in a 7 by 4 inches blank doc in photoshop](https://i.stack.imgur.com/aczPK.png)

as you can see the logo are both crisp even if placed in documents with a great size difference.

Photoshop is just a better program to create mockups in general since all elements such as images and fonts can be easily edited.

I hope this answers your question, have fun!