[QUESTION] please read

OK so sorry for the stupidity but i have to ask this.

SO im guessing the way people spam forums, blogs, directories etc etc is buying ANOTHER domain; not using the MAIN domain but using the forwarded domain.. but using your server but having lets say adult.php(your forwarded domain site) forward to your index.php(your main site).

for example..(i know google wont reference this because they dont like porn) btw this is not my real site.

Say i have a site its called adultwhateveryouwant.com
i buy the domain pornforyoumesohorny.com
i forward the pornforyou to adultwhateveryouwant.com
i spam the forms, blogs, guest books etc etc with the pornforyou domain and that will redirect its self to my main domain adultwhateveryou.com.

now my question is do i buy a regular host for this or do i just host it on my server...im a little confused on this subject.. if i was to guess i would just host it on the server and just use my own pages for the doorway pages or w.e.

does any mind clearing this up?

I know that some people do a little twist. They use trusted domains to spam. What i mean:
Make a profile in Orkut (for example). There in your profile you can make a page. Put the keyword rich text there + a lot of anchored links. Start spam for your profile. This way you have a chance to go to first page of google easily (with the profile) + you get back links to your site. You can use a lot of sites for this. You can also use google groups. I've seen this. I am not just writing crap. There was a Orkut profile in the first page for the word "buy v1@gra" (the real word).