Is there a difference if someone was to purchase 1 homepage link versus sitewide links? How would it effect the SERPs? Would it make a difference if I had 1 link or 100 links pointing to my site from 1 particular site?
Not much for serps anymore. However, if you are after actual traffic, there's a lot more chance of getting a link on 100 pages than 1.
Not in my experience. I am of the opinion that the major search engines mostly just count one link per site to the same page. I believe that it could then be a page other than the homepage, though, which may give less benefit. Of course, a lot of this is just a guess, though, since I do not have any way to know for certain, and it could be (and most likely is) handled differently (at least to some extent) by different engines.
Sitewide is pretty pointless. I a link is a link. Unless each page on the website has a different PR or what not it doesn't really matter. Besides - PR is nothing nowdays.
I would say you should treat links the same way you treat other advertising. So the more you can have for the same price, the better.
i havnt noticed anything bad about having a sitewide link i go for sitewides.. traffic value = great i am often getting clicks from very deep detailed pages i have sitewides at but u still cant beat one single highly targetted naturally placed incontent link IMO.. well maybe if you had 2 of them