Though I can't speak for everyone, I do know that 
I first got into the hobby [when I was a college 
student] because (a) I had a show that I liked; 
and (b) I thought it was immensely cool to have a 
piece of production art that was used in its 
filming. 

My first cel was a whimsy purchase off of eBay 
('98?). I bought it, I admired it when it 
arrived, and it sat half-forgotten on a shelf 
afterwards. :o) Two years later, I went to my 
first convention, and just so happened to find 
two more cels from the series I liked. With the 
exception of a pencilboard, it was the only thing 
in the dealer's room that dealt with that 
particular series (which has only just now had 
its v. 1 R1 DVD release as of January). Shortly 
afterwards, I got sucked into my most intense 
period of growth, which was mostly fueled by a 
desire to not just have a collection, but to have 
a *good* collection, both in terms of scope and 
of character representation.

So for me, that's how it went... a spontaneous 
purchase led to other spontaneous purchases, and 
it eventually led into collecting for the sake of 
the collection itself.

I think that any art is going to compete against 
$5 posters. I pay attention to convention 
artshows, and I find that the convention 
demographic is much more likely to pay $5-$10 for 
a poster that's the same poster that 50,000 other 
people have--- or a shitajiki that 10,000 other 
people have--- rather than pay $10, $15, $20, and 
up for a piece of nice, original fanart in the 
artshow. And for those who do buy it, they do 
tend to be older--- late 20's, 30's, sometimes 
40's. Student-aged con attendees are not the 
driving force behind artshows. :o)

I would think that similar parallels may be drawn 
for cel vending. Younger people concentrate more 
on the image and the price rather than less-
easily-quantifiable values, such as the perceived 
value of original artwork. Mass-produced art is 
cheap, and that can lead to the general 
impression that all art should be cheap. Art, 
after all, is a luxury... and cels by their 
nature do not lend themselves to being readily 
enjoyable. The more I love and value a cel, the 
more likely I am to keep it shut away in a binder 
for its own sake... and who wants to buy art just 
to put it in a closet? :o) That's half the fun of 
an online gallery... it's a nice place to remind 
yourself what you have in your binders. After 
all, how many of us ogle our cels every day? 
Every week? Every month? I know I go through my 
binders much less frequently than that...

Disney and Hanna Barbera are going to be good 
investments, comparatively speaking, because they 
have their own built-in value by their very 
nature. A junk shot from Fantasia is probably 
going to go for more than a good shot from 
Detective Conan. :o)

If I was going to go into the anime business, I 
would probably concentrate more on the 
DVD/graphic novel aspect of it. I do hear that 
translated manga is one of the few areas of 
publishing that is actually experiencing growth 
right now... With the DVDs and the graphic 
novels, you're more likely to appeal to the 
lowest common denominator, and you have the added 
benefit of having a commonly recognized product, 
something that is useful and can be enjoyed, and 
you have a built-in audience. On the other hand, 
the people you want to appeal to-- the ones who 
buy large quantities frequently-- are very savvy 
about their shopping. If you set yourself up to 
sell at full retail, it will probably not be a 
very successful venture. I think RightStuf has a 
very good business model as far as that is 
concerned. 

For graphic novels, you might look into a service 
like Netflix... they can get very expensive, if 
you have a 10, 20, 30, 40+ -volume series at 
$10/volume (full retail). And there are so many 
good titles coming out, it's impossible to 
collect everything. So a subscription-based 
lending-library service might be useful. It's 
something I've thought about getting into, if I 
felt like it. :o) 

Another thing you might look into is offering a 
translation service, if you're fluent. The 
doujinshi market always appreciates people who 
offer their services. It's a little difficult to 
approach most "regular" translation services, 
often because the content can be a bit 
embarrassing, or because the pricing structure is 
more suited towards doing translations for 
international businessmen and legal documents, 
rather than the ramblings of mangaka on their 
dustjackets. :o)  

But in general, you ought to find a niche and 
fill it. How long have you been in the anime 
fandom? During that time, what sort of things 
(services? products?) have you wished existed? 
For me, the big thing I always wanted was manga 
in English... and some people came and filled 
that niche, and they certainly have my 
business. :o) But there are still plenty of 
niches left to stake a claim on.