Back about 2003, I decided to sell my 15+ years sitting in boxes HO models including a good number of brass trolleys, quality track, unopened plastic as well as 'craftsman' building kits, etc. It was also the impetus to try digital photography after 40+ years shooting film.
I naturally researched what I might get on ebay, as that looked like the easiest way to get the best 'coverage', global, in fact! So, taking photos of 5-10 products each week, then learning the freebie very early Photoshop that came with my camera, I then spent some time looking at 'sold' items on ebay.
Perhaps the biggest surprises came when items that I expected to fetch a good price didn't. And other items, from built Athearn kits I'd weathered and equipped with Kadees and Central Valley trucks went for considerably more than what I paid for them. The HO brass trolleys, most were professionally painted, generally went for 4-5 times what I had paid for them in the 70s.
Lessons learned:
1. Decide whether it's more important to get 'top dollar' or 'get it gone' at a good price, 5% or so less than what others are getting for identical items. I always wanted it gone.
2. Back then, ebay did not have a 'buy it now' feature, so everything was an auction, 3, 7 or 10 days, as I recall. I typically started at 60% of what I hoped to get. That way I knew it would sell.
3. I had roughly 150 'shake the box' assembled plastic railcars. I sold them in lots of 3-5, to make them gone faster as well as reduce the number of packages I had to ship.
4. You'll have to become adept at packing and shipping, even with the original boxes for all my rolling stock. You'll certainly remember the 'savage airline baggage handlers' (a gorilla) advertisements 30-40 years ago for a luggage company. Having worked as a package delivery driver and later package handler (loading and unloading trailers) at a global shipping company, I can tell you from experience that if it 'moves' inside the package (or original box), good chance it will get broken. Plan on stuffing toilet paper into original boxes, and using 'used' packing materials from bubble wrap to boxes. Be sure to remove or use a marker to obliterate all labels on boxes prior to reusing them. The US Postal Service provides free priority mail boxes that are designed to be used as such. Having to buy bubble wrap and/or boxes is guaranteed to THROW AWAY any hopes for making a profit!
Buy clear shipping tape and an appropriate dispenser. I buy Duck brand shipping tape at Walmart. Don't waste your money buying 3M shipping tape, etc. I buy padded envelopes of multiple sizes online as well. By the way, buying stuff online at Walmart and Amazon is a great way to build up a supply of boxes and 'stuffing'. I buy all my over the counter meds as well as some non-perishable food items at Walmart online using my Amtrak credit card for points!
I still sell on ebay now and then. The ebay 'cut' from sales price have gone from 2-3% to 15% on average these days! Shipping costs have tripled (or worse) the past 15 years or so! They used to charge a 'listing fee' of about 1% the 'listing price' and then a 'sale price fee' of about 2%. Payment was by check or money order. They added setting a 'reserve' (minimum bid price to sell) for 10 cents, but now it's 75 cents or more...I learned the hard way to avoid that 10 years ago.
These days, I usually sell everything as 'buy it now', sometimes with 'or offer' if it's over $75 or so (camera gear, electronics, etc), No more auctions unless I don't have a clue about a good price. Buy-it-now used to 'expire' after 30 days, but now anything unsold gets automatically 'renewed' after 30 days. I routinely start at maybe 95% of what I think is a good price for an item and drop it 2-3% after the first day, maybe another 2-3% after a week, and maybe more after 2 weeks. Any 'or offer' items allow you to set a 'minimum' price to automatically accept an offer, as well as an 'automatic reject' amount. I can guarantee from experience that there's always a low-ball offer or two the first day from those looking to resell it at a decent profit...camera gear especially.
Ebay used to not charge 'final sales price fee' that included any shipping costs listed. When I was building computers for friends, I'd buy a used CPU or RAM for $5 with $25 shipping cost (in the listing) as the seller would only be charged a percentage of selling cost. Ebay finally finally figured things out and now both together are used to determine the final fee (12-13% these days!) Their relationship with Paypal changed when they bought out Paypal about 12 years ago, only to spin it off 7-8 years ago, then make it nearly impossible to pay with Paypal and then finally reintegrated it about 2 years ago, but for most buyers, they now pay directly through Ebay. Of course, Ebay now gets the 3% or so that Paypal would be getting. ALSO...as a seller, moving money from Paypal to my bank account was typically 48 hours after I entered the transfer request. On ebay, THEY take their sweet time before starting to move your money to you and now it's 5-6 days after the sale before I get the money...multiple items in a single deposit is common. Oh yea...and now Ebay pockets the money for shipping then bills you later...long after they've sent you money for the sold item. In short, Ebay now gets the 'float' of maybe a billion dollars per day which can amount to 100s of thousands of dollars of interest THEY get on YOUR money!
One of my friends used to sell some of his 'junk' on ebay but has since ceased. He and I both have sold some of our basement 'junk' and got decent money. But the big lesson learned about 10 years ago was if you don't think you'll get $5 as a selling price, throw the item away. It takes just as long to take pictures, create an ebay listing with pictures, box it up, and take it to the post office or wherever for a $100 item as a $5 item. These days, anything less than $20 is a waste of time in my book...and I've been retired for 7 years! Between high shipping costs, including SLOOOWWWW delivery (5 days for 2 day priority mail 1000 miles a couple weeks ago, and 2+ WEEKS for priority mail 9 days before last Christmas) and including shipping materials, makes $20 about a break even sales price in my book. The low-expected prices for Athearn box cars was why I bundled them into threes and fives...to get a 'worthwhile' total price.
Also, RR books are near worthless these days. Books that I had that pre-Ebay days would garner $150 or so, fail to sell at $35 these days. Even railroadiana such as switch locks with keys, etc, prices have dropped a LOT in the past 20 years! I had some RR books down to $7 with free shipping and they still didn't sell. I tossed 'em. By the way, if you're selling books or slides, be sure to ship them using 'media mail' rate (available on ebay if you click the 'see all options' shipping, but NOT available at USPS.COM. Go figure.) Media mail is considerably less costly than first class or priority mail, but is for printed or recorded media only!.
Also...There's also crooks out there that will buy your item, advise that it's damaged in transit or was not working up front and demand a refund. When selling used computer parts such as CPUs and RAM, I learned to put a small scratch or Sharpie mark on each item and make sure that shows up in the pictures on ebay. I had one buyer pull that on me with 2 sticks of RAM that sold for $150 or so. He returned them and I didn't see the tiny Sharpie marks, took pictures of his substituted RAM, wrote him so and sent his garbage back to him. I never got a complaint from that clown.
Also, a disappointment...only about 30-40% of ebay buyers ever leave feedback.
So, if you have lots of time to kill or need something to keep you busy, selling on Ebay as a great way to fill the hours.
Plan B: I know 5-6 years ago there was a number of 'we sell on Ebay for you' shops pop up online and in town. That would be a trouble-free way to sell your collection. I don't know if they still exist as between ebay fees and shipping costs, throw in their costs, I'd venture you'll get about 50% of the sale price of the items, assuming they're trustworthy. I even thought about opening an I-sell-4-U place, but the record keeping needed to keep customers, buyers, and the IRS happy makes it not worthwhile in my opinion.
In my opinion, the days of 'send SSAE for listing' advertising in magazines is long past. Even hobby shops with model RR equipment are nearly extinct. Everything these days goes online. Also, as I found selling brass trolley models, at those prices, people model and buy what they remember. How many of us remember seeing street cars or steam engines? For what it's worth, I still check the prices for Suydam CNS&M models on ebay maybe once per year or so and the prices they're getting today is not much higher than what I was getting 15-18 years ago!
Plan C: Sell it all as a few (under 5) lots to someone knowledgeable in what the items might be worth and willing to sell them on ebay or <whereever>. But remember, the few potential buyers would low ball it ensuring a reasonable profit for their time and investment.