Affiliate Marketing Secrets

I see sites that make great income from providing services, but dont have income from affiliate or advertisement, then I see sites that are the opposite.
Why can’t websites generate profits from all of the following at the same time :
Advertising Sales
Product or Service Sales
Affiliate Income

I want to start a new site and would like to know what earns best when using adsense.
Maybe Iphone covers, electronic gadgets, biblical stuff? Anyone knows?
Also, not just the best paid, but also with a decent volume of advertisers.
Thanks!

I’m trying to get some information about creating a social network with buddypress. I’m not talking about creating another Facebook but my site would be more like a linkedin website for a niche community. So I would have features such as profiles, messages, employer page and employees page, contacts, chat. Is buddypress good platform for a website like that?

I’ve seen SEM firms like google willing to promote your site for $500 – $150,000!!! Or I can just hiring an individual SEO who can help promote my site for me. And of course, do my research making sure the individual SEO will be doing their job bringing traffic etc. My question is besides one being bigger than the other, which should be good for affiliate websites? Would SEM be good for larger corporations like Redbull since they have all the money to spend for marketing & advertising like $150K?

so i have a new website and i added my first new post to the already existing 2 and on the home page the post doesnt have an image like the others do and i havnt got a clue how to give it one, can someone help me, you can see it here www.affiliatetipps.info its the top post in the affiliates for beginners sections on the home page
www.affiliatetipps.info

www.crazydomains.in
Is it reliable?