Z has some great points.
As a person who sells and buys a lot on ebay.....here are my answers.
Is there anyone else on here that does this that can give any advice? Some of the main questions I wanted to ask about are:
1. Is it profitable? If so, how much can you make?
Obviously this is determined by what you mean by "profitable". If you mean a junk bit that you will just throw away, then technically if you make 10 cents off it, its a relative profit.
A lot of bits on ebay go for dirt - where as some very specific bits (grav guns for example right now) go for quite a lot per bit.
Selling off old stuff you don't need its easy to make money - but this is 100% different than buying a kit, parting it out, and hoping to make back more than what you paid.
(you have to pay for your time and investment). Look at the various bit vendors, see what they are charging, or more accurately, do search on some of your bits and look for closed auctions that actually sold.
Many people make the mistake of thinking just because someone lists a specific part/kit for $X, that people actually buy them.
For example, I am getting ready to list up two kits I have in my closet - I won't be using them, so am going to sell them.
I do some research on what they have recently been selling at, and what they are being offered at, and how many of them are up (you DONT want to list something as an auction when there are 20 of them up).
I then figure out exactly how much it will weigh in the mailing package, so I can use the ebay tool (in the selling menus) to get a shipping cost.
If I don't have a package, I need to add that into the cost.
2. Is it GW legal to sell bits on eBay as a business?
What Z said. Now, you just said...."as a business".
Selling extra bits is one thing, as a business ...you need a LOT of research to even consider it, and a lot of capital to get started.
Personally, I would suggest against even considering it.
3. How would you solve the problem of not having to go the post office every 5 minutes?
I try to list all my auctions to end on the same day.
Also, if this is a business - then your time is a resource to be paid for - this is a key fact most people miss when starting a business.
4. Any other general advice/tips?
* get good pictures, people want pictures
* don't pad your price in your shipping - it annoys people.
* do research on what the going (i.e. successful sold auctions are) for the specific things you are selling, and make sure they are recent. For example, before the new tau codex dropped, the old broadsides typically sold for over $30 each...after the new codex dropped....people are lucky to sell them for $15.
* If these are bits you don't want or use, what makes you think others will want them enough to pay for something that is worth your while. Me? My time is too valuable, I don't even bother to list things that I don't think I can sell for at least $15...the pictures, listing, packaging, postage etc. does not make it worth it. I can mow my neighbors lawn in less time and make more.
* If you are just selling left over stuff, any and can make a few bucks on the side, thats great! If you are contemplating starting a business doing this, do a lot of research, make a business plan, and maybe take a class in accounting at a local community collage.
* get tracking on your shipments.
* try buy it now - a lot people don't like waiting. Look at the other buy it now auctions or what the average final selling price is on the recently completed auctions to help you set a price.
* look at the competition - buttet bits, horde o bits, bits world, etc all do this already - they sell THOUSANDS of bits a month (or a lot more).
* send a thank you note, or at least a message indicating when you shipped, it is courteous and will help your feedback rating.
best of luck, and if you have any other specific questions....