I am new to RVing as well, so the best advice I could give is the following.
I started out by checking RV ads to get an idea of what was out there, floor plans, features, etc that I'd want or need. I went to a few dealers and sellers. This enabled me to actually see and be inside several different units. On the ones I liked, I researched the models and equipment brands & types in them. It helped rule out or make me add to my list specific, types, makes, models, features etc. For example, I'm a big guy and I didn't like the way a lot of floors were extremely squishy under my feet in some, but not all brand new light weight TTs. I would have never known this would be a possible issue without having actually been in a few different makes / models.
As for learning what to look out for, I watched a lot of youtube videos and read a lot of info guides found by googling as well as the forums. This helped me learn what to look out for, and helped me make a list of must haves, wants, etc. Kind of like you would do when looking to buy a house or car.
This is how it worked out for me and my family of 6. The difference between you and I is merely our tow vehicles. I have a 1 ton diesel, so weight was not a huge issue for me. I did, however, want it to be tow-able with a 2500 suv if possible, which ruled out 5ers.
I started out thinking that a 26ft, 7k (loaded) pound TT would do well. We ended up with a 31ft, 9k pound (loaded) 31SQB model. The extra size and weight allows for sleeping up to 11 people. It sleeps 7 without using the sofa nor dinette. Not having to use the sofa nor the dinette for everyday sleeping, a MUST have. Also a large bathroom, with plenty of room for me, being big and having had recent spinal fusion surgery, this too was a MAJOR MUST have for us.
We did make other concessions on things that can be added, remedied later, or even traded off for other things.
For instance, I lost some outside storage, and got smaller bunks, but gained a few huge items:
1. A small but useful outdoor kitchen which wasn't even on my radar, but I expect will be used often as per my wife demanding I cook... BONUS is there is another refer (120AC only) located in it. This will keep the beers close while I cook lol. It also makes up for the 6cf one inside that is not the 8cf I wanted.
2. A very large wardrobe (small slide out) in the bunk room for my teenage boys to place their clothing. BONUS is this makes their bunk room rather large for entertaining themselves AND it even came with a TV in the room (in addition to the living area one) as well.
3. It worked out well that this TT has one of the most roomy bathrooms we'd seen. BONUS is a second entry to it from outside and the main entry is in the living area as opposed to the bedroom, like most other models.
Basically, educate yourself on what's out there, what features you need or want, as well as what you'd like to have, but can live without.
Most importantly, to us anyway, is that it needs to "feel" right. My wife and I loved another TT that we visited, but my wife felt something "off" about it (she attributes it to being brown inside). We both felt right as soon as we walked into our TT, we didn't discuss the feeling we shared until a while later. And we compared pictures of the other TT, only to see that it had less brown then the one we purchased. LOL
