@Colletta0
I specialise in long term stays. I cannot answer all your questions as laws will vary from location to location and I don't know about tenant's rights where you are. I have also never had a long term guest not make the monthly payments, but it certainly is a risk and yes, I think the Airbnb security deposit is fairly meaningless.
RE cleaning, I don't charge a cleaning fee, just incorporate it into my nightly rate, so it doesn't cost me any more to host long term than short term. Also, some short stay guests leave a lot more mess to clean up than some long term ones. It just depends on the individual. I offer to clean guests rooms (I host private rooms in my own home) for a fee during their stay. This is optional. They can choose to do it themselves and I provide extra bedlinen and towels so they can change and wash these when convenient if they don't want to pay me to do it. However, I have learnt to stress that they must actually keep the place clean and wash bedlinen/towels if they are here for a long time. I provide cleaning products.
I provide the same supplies as I would for short term stays. The guests do get a long term discount, but it's not huge, so I don't feel that I should reduce what is on offer. The only thing I ask them to buy themselves is laundry detergent/softener. I also find that long term guests almost always buy their own toiletries, so I actually go through less of these than with a series of short stays.
Your situation is a bit different though as I don't provide breakfast, only tea, coffee, sugar, honey, hot chocolate, some cereals, salt, pepper, oil, spices etc. Again, I find that most long term guests hardly use these, except maybe the salt, pepper and sometimes oil or tea, but a lot of them even buy their own oil or teas and leave them here for the next guests. All in all, I need far fewer supplies than when I was hosting short term. The only thing I don't buy less of is toilet paper!