FRAMES == BAD
SEO
Most spiders have problems indexing framed sites, so it's tough, if not impossible, to gain any ground in search engine results. That's another reason why you don't see framed sites all over the place.
I've got about 10 domains registered on one site and about 8 for another site. Basically, they'll help snag traffic from those who surf by entering random URLS in the address bar. I'm not sure it will help you gain positions in the search engine results but it's not going to hurt.
Strategically it's a good move in that your competitors can't use those domains to build competing sites.
Register as many domain names as you like but you'd be much better off to use 301 redirects to point users to your main site where they'll see your regular domain name.
Using framed content without redirects, I'd assume that you'd put your site at risk of being penalized for duplicate content or worse, you'll confuse and/or annoy your users. Additionally, most reputable web directories won't post links to sites that do these sorts of things.
Contact your server admin or hosting provider for assistance in registering domain names and setting up the domain redirects.
I don't utilize Adsense or Adwords PPC campaigns and my sites rank very well for their targeted keywords/phrases across the major search engines and in very competitive playing fields. Best of all, traffic volumes are increasing steadily.
If you need the big numbers right out of the gate, use Adsense/Adwords initially but build your site using solid
SEO techniques to acquire sustainable, reliable traffic and you'll be miles ahead in the long run.
That's my .02