Looking to buy, bunkhouse ~26ft, all advice welcome

5 persons? Slide, for sure. Everything Matt says, I agree with. Cooking space and privacy might be looked at too. Where's that last kid going to eat?
I vote for used. You'll save thousands, if not ten thousand dollars. If you saw my trailer, you'd understand.

Hi Amandasaylor, welcome to the foum. You'll find quite a variety of opinions on your questions from all of us. One thing I can suggest to get the best answer is to give us the make and model of your perspective tow vehicle. Also if it's a newer model open the drivers door and see if there is a white and yellow sticker on the doorjamb. If so you should find a statement saying something to the effect of "maximum capacity for all occupants and cargo is xxxx. If that sticker is there please give us that number as well.

As far as your actual posted needs:
Quality built!<-- most important. Tell me the brand(s) that stay out of the shop! Unfortunately most of the trailers, heck most RV's for that matter are built the same, fast and cheap. You can maybe look for solid wood drawer and door fronts. Some of the more expensive have complete solid wood cabinets as well as the doors and drawers. I have had my Jayco since 2005 and it has served me well with very few issues. If and when I buy again I will definitely look at Jayco again.

Bunk house
23 to 26ish ft (advertised length, I know they are truly longer with hitch) Mine is a 27BH (BH for bunkhouse) but it's 30 feet bumper to tongue. I like the layout even with 4 boys. When they were small two shared the full size bottom bunk and one on the jacknife sofa. Now that they are older one or more no longer camps with me so the bedding isn't an issue.

Useful layout with storage!I like the passthrough front storage on mine. The only problem is it's easy to wind up with a whole ton of stuff in the trailer that you just never use. So every year or two you should try to go through everything and remove the unneeded stuff.

A slide, I think. Unless theres a big reason not to.A slide definitely adds some usable room. But it also can add 1,000lbs to the trailer. Which may or may not be a problem. If you do look at slides make sure you can access things like the bathroom and maybe the refrigerator with the slide all the way closed. This may or may not matter to you. But it sill be good to know so it's not a surprise later.

New or used? What say you...Mine was new, but I have no problem going used. Going used will definitely make it more affordable. But RV's leak and leaks can be catastrophic for them. So you need to check everywhere on the floor for soft spots or discoloration. Also look in the corners of all the top cabinets for water staining. For used you might want to search for a mobile RV repair person and pay them to look your prospective purchase over before signing anything.

I heard that straight toilet plumbing is the best for negating leaks and a mess down the road...true? Who has that in a TT? I'll bet that the straight plumbing is more common than plumbing with a bend in it. It's easy enough to figure out though. Just hold the toilet flush valve open and look down with a flashlight. Make sure you firmly hold onto the flashlight and I would never use my smart phone in case it got dropped.

Last bit of advice. On any prospective trailer go into the bathroom, close the door and make sure you have enough room to do your business. Don't just sit down and then stand up. Take a minute to relax and picture if you actually have enough room.

A slide makes a smaller RV "big" at the campground. I wouldn't buy an RV without at least one slide. For your first purchase...to determine if you really like RVing and to avoid substantial depreciation...used might be better. Unfortunately, no RVs stay out of the shop. The key is a close inspection, using every system and ALL repairs before you put any money down. Consider a pro inspection before you buy...or at least a very experienced RV friend. Get ON the roof and underneath with a flashlight too. Be careful to determine if your tow vehicle is adequate...not just GVWR...payload!