What is better?

A complete site with a business directory, classifieds, jobs and news

or

different sites with different domains and different layouts for each category?

In my opinion you would be better going with different domains and layouts for each topic. When a person comes to a website they are generally looking for something specific. Making the website spread out to a number of different subjects can confuse the viewer as well as make it harder for SEO. However, this really depends on the subject that you are doing. Obviously you wouldn't want to make a website based on two completely different topics, it just doesn't make sense. So long as the topics that you have on your website are closely related in such a way, you may not have any trouble with functionality, but the SEO may be a little trickier.

make it all in one and if the traffic gets to overloading the server then put each section on it's own subdomain / account

Put it on the same website. You then have 3 angles to advertise your website from. So long as all of the topics are closely related, like they are, I do not see a point in putting them on 3 separate domains.

For SEO purposes it would make more sense to have a single website for each of these. As this will allow you to dig deeper down into your niche market and receive a better listing in the engines along with a better bounce rate for the site as the information the people where searching for will be more relevant to what is on the site.
Ask yourself this when you go to a site that has multiple topics how likely are you to trust the quality of the content on the site as opposed to a site that is built soley around the term you where searching for?

I agree with them, just put it all it one website and the other links will be in your subdomain level.

thanks all.

I personally would suggest having one domain name and make catorgies off the domain name. This will alow for you to put more advertising money into the one website and make that your main focus. Best of luck!

You have a very useful and informative post. I am trying to learn how to make website, reading other blogger replies give me idea how to do it.

That is a very good question. My company does most of our website stuff now internally, so had to ask ourselves somewhat similar questions. We decided to go with different sites, but narrowed it down to just 2 big categories...So its not quite an SEO nightmare, but 1 is easier than 2...

I have tried a few of these get paid for surveys/emails etc, and I have struggled to make decent money with any of them.Now maybe there are bona-fide sites out there but don't expect millions overnight. If you have considered starting working from home then why not broaden your horizons and learn to start your own affiliate or marketing business.

I would agree with ThePixel. Use one domain name, however place different parts of the site into different categories. In terms of SEO you would also better choose subcategories.

According to me you must concentrate on one site and yeah definitely make categories of tat domain.

I recently did a website for a customer with NINE different businesses under the same umbrella site - as Kelevraco said, this may mean that people don't trust a "jack of all trades" website as much as they would trust a specialist website. From the customers point of view, he only has to pay to design and host one website and any links he gets to one page will bump up the link juice flowing to other pages.

I think i would go for one site instead of having loads of domains etc. It starts to complicate things