I'm not sure what you mean about "which business model to pick." I have three different types of ebay sites; phpbay sites, mcjiffy sites and my own scraping of an ebay rss search feed.
The easiest one to set up was probably the mcjiffy one. The best looking ones, that look most like a "real site" are the php bay sites. The one that was most customizable but also the most pain in the ass to set up was the one I coded myself ( thus the success of phpbaypro and mcjiffy ).
I can't really brag about the buckets of cash that are rolling in because my niche selection / keyword selection skilz suck deliguy's balls. No matter what you pick, your projects are likely to pull in more money than mine if you can nail those things down.
Hint: "used louis l'amour paperbacks" isn't a great money-making niche.
Just starting out, I'd recommend wordpress + the phpbaypro plugin. That combination will give you the ability to easily add content and easily link to auctions.