Ebay is wonderful because many of the sellers there seem to have it down as far as representing a rig with photos. So you can really get a sense of what a rig looks like inside without seeing it in person.
RVT, like Ebay, is thorough because it gives listings from across the US, and is only RVs.
Craigslist is better for local listings and private buyers, IMO, but has also been a great resource for investigating rigs. Just with many less photos.
Sadly, dealers seem to be the best at taking ALL the photos, because they've done it so many times and know what people want to know. Yes, I really DO want to see that floor, and what all the cabinets look like INSIDE, and what the storage bins look like INSIDE. You just really CANNOT take too many photos of an RV - there are so many different things that photos can show, sometimes even better than looking at it in person, believe it or not. Because in person you get swept up with being in the rig, and the seller, be it private or dealer, will be talking to you and distracting you from really taking a close look. With photos, you can look all you want, and there's no one taking your attention from what you're seeing.
Of course, you can't SMELL through the photos, or REALLY feel what it's like to walk through that pass way, or shower in that shower, so seeing rigs in person is definitely valuable, too. Of course! And if you can manage to get a test drive, all the better, because driving comfort is SO important!
With my limited spoons, and actually seeing RVs in person being really really difficult on me (salesmen LOVE cologne! And used RVs tend to have lots of interesting smells - spending a day in them takes me out for a week), I have LOVED the internet options that are out there. We only go to look if there is a rig we're REALLY interested in - and of course when there is an RV show.
All of this looking around has given me an idea abut what rigs have floor plans we like, and has even let me know what we prefer. Going to an RV show and looking at different rigs also helped us feel a sense of the space and design to give us an idea of the type we want.
We already decided we want a diesel pusher. They can be more expensive to maintain, but they are also more durable and long-lasting and in our opinions, more suited to full-time living. The engine is in the back which makes the drive quieter (we can talk to each other without walkie-talkies!), and also adds to the ability to get up those hills. Diesel engines can last a million miles, so mileage on a used diesel, at least engine-wise, isn't very relevant. And they tend to have a much better resale value.
~ door in front of rig, for maximum living room space
~ 2 slides, for more room when parked
~ counter space! what we love about the bounder is see up there? pull-out extra counter space! since we don't really eat out the kitchen is of utmost importance. I gotta have space for my Vitamix!
~ big fridge - this is something we could replace ourselves relatively easy, but man it would be great to have it already done for us
~ an oven. We don't do microwaves, and I don't know enough about convection microwaves to feel that they're safe (for us) to use. So I gotta have an oven.
~ washer/dryer or at least the space and hookups for them. Again, with my chemical sensitivity, is important to have our own.
~ ability to convert bed to King (almost no rigs in our price range come with a king bed, but most of them come with a queen and the modifiable space to upgrade it ourselves
~ big ol' closets in the BR (which can be converted to a bunk/play area for K)
~ enough extra closets in BR that converting the big closet won't lose all of our space for clothing
~ a good location for the flat-screen TV in the living room. In an RV where space is at a premium, it's difficult to find a good location for the TV. And given that ours is usually also hooked up to the gaming systems and HDD drive, we need space for those, too. Sometimes this might require some modification.
~ relative ease of converting carpet to wood floors. Bonus if this has already happened - it's rare, and something we expect to be doing ourselves. And by 'ourselves', I mean my husband will do it.
Then there are mechanical things as well, but inside, the space we will be living in, that is important space!
Mechanically we ask things like:
~ Have the recalls been fixed (there are a few recalls for this model and year - minor things that the dealerships fix for free, like fridges)
~ What type of generator and how many hours are on it (this should be included in the description but often isn't)
~ How old are the tires (they need replacing about every 10 years even with low miles because the UV rays can break them down - this might be changed if they were stored inside, but I don't really know)
We got a lot of great information about buying a used motorhome from the book "Buying a Used Motorhome" by Bill Myers
Right now the Kindle edition is only $2.99! And it was so worth it! It gave us so much to think about that wouldn't have occurred to us had we just been figuring it out on our own.