I found this cage on craigslist for $110, it is very clean (or at least it looks that way) I just had a few questions, it has a rounded top, is that okay for gliders? Also, I'm pretty sure it was used for birds previously, is it still safe to use for gliders?
(It wouldn't allow me to upload a picture)

Usually bird cages are safe for gliders. You do need to be certain that bar spacing is not over 1/2". Also, size and sturdiness are important, some bird cages can be a bit flimsy and a small size for sugar gliders. Flight cages are usually larger, but can still be flimsy/ not sturdy. Door style would be the next thing you'd want to check on, they'll need to be a decent size for access for cleaning and furnishing, and the kind that slide up and down can be dangerous if not carefull. Swing-open doors are best, and sturdy locks are important as well.

If going for a used cage, watch for rust.

Thank you, that is all very valuable information. :)
It is a great sized cage, 43" tall, 28" wide, and 20" deep. In the pictures it does not appear to have any rust but I will make sure of that before I get the cage (if I get it). It has a large swing-open door, but only one. Is that something I should worry about? It is a very large door but is it important to have multiple doors? Also, I'm mainly worried about the fact that it is a dome like top. Rather than a square shape, it is rounded at the top. Would that be an issue? I was think I could find some safe, small, shelf like things to hang more toys. Would that be an okay thing to do?
Thank you!

The dimensions sound okay, do you know the bar spacing.

I'm sorry that I wasn't more clear stating the things that are important in a cage, meaning the dome shape shouldn't be an issue. If you can't find shelves, no worries, you can make braided fleece vines that can stretch taught across front to back or side to side if you wish to hang more toys from (must be taught). There are also perches that may fit across the cage, these you can hang toys from or better yet make a fleece sleeve with loops to hang toys from.

One large door is plenty, as long as you can access inside to clean the cage. Larger glider accessories such as exercise wheels (make sure to get glider-safe wheels) and other large toys will require a large door, so as long as you can access for cleaning, those should fit through just fine.

The onlyissue i see with that is the pouches. They need pouches to sleep in and its better off to have them hanging, but if you get a cage with shelves youll be able to hang the pouches on that. When i ferst got my gliders the breeder brought them in a fleece hat, he said i could keep it so i put the hat on the floor in the cage, but i would find sometimes that they would be in the hat on the floor rather than the hanging pouches, so i hung the hat for them and thats the onlyu place they sleep in regularly now.

That's cute!

Actually though, pouches can be, and are often hung along the sides of the cage. They don't have to be hung from the roof, though can be. Some hang them on the door of the cage.

I personally keep mine hung in the corner. I've had hung them around in different ways over the years, but I find they're less disturbed in the morning after they go to bed and I want to take out food dishes and do daily tidying up. I can access them easily in the front left (facing) corner if I want or need to.

Even if you wanted to, a braided fleece vine that is hung taught enough could be used to hang a pouch from, if you can't find a properly fitted shelf.

The main concerns about a cage are: bar spacing, size of cage, sturdiness, and style and size of the door(s).