I have plastic and wood shelves with a deep plastic pan in the bottom with recycled paper bedding. I’ve been looking into using fleece too but I know my rats will probably chew it. Luckily I’m pretty creative, crafty and have a sewing machine so I can make stuff myself. I read someone started using bath mats on the big sections of their rat cage and it worked well (you should be able to find the post on here) I’m going to try it after I rebuild the base of my cage since they chewed two holes in each corner (had 8 rats, so easily done when they double up). I’m not going to get a new cage because I had just got it a year ago and not able to spend the money to get a new one (which would be the double Critter Nation). I clean the shelves often so haven’t put any liners on them yet. Mine don’t seem to be interested in being potty trained unfortunately but I still keep a pan in there since they occasionally use it. If you try potty training use different substrate than used on the floor and sometimes a pee rock helps. As for fleece you can go to craft/fabric stores and get remnants where they sell fabric, look for coupons for that store too. If you know of someone that has a sewing machine it’s easy to make hammocks and ‘shelves’, maybe they can show you how to do it and then you could get a cheap machine that does straight and zigzag stitch (they don’t have to be perfect they’ll be chewed up anyway). For hooks to hang try to get stainless steel they won’t rust and last longer than plain metal ones. Make sure you have plenty of things for them to do and things to chew on. You can make rope bridges or 'hammocks'. Make sure you have at least 2 rats at all times, they’re very social. Don't completely clean the cage, leave some things so as to make them not scent their stuff again. Usually the cage is deep cleaned once a month, a few times a week cloth stuff is washed and shelvings cleaned daily or every other depending on material. Try to clean up pee/poop daily. Don't use scented detergent or cleaning stuff- vinegar, baking soda and unscented natural soap is all that's really needed to clean everything. Rats do not need baths, only wipe with warm water on small cloth if they smell. There's all kinds of things you can get and make for their cage or to play with/in/on that's cheaper than buying things made specifically for critters. Just be mindful of toes catching and anything wood being nontoxic to them. I do recommend reading a lot of the posts on here in each category, they’re helpful. Also health and food is important too. If you want more info from me you can ask to reply here or pm me. Rats are great pets and can be inexpensive if you use go for creative and thrifty.