@Miki5 - when we've hosted long term we do the following:
1. We INSIST on a once-a-week cleaning of the guest's room/bath and a linen change. We want to be able to inspect the space weekly to make sure there is no damage, problems, or rules violations. This also enables us to keep up with the cleanliness of the space so that, after a few months, we're not cleaning weeks of filth off shelves, the floor, and in the bathroom - just think of the HAIR! The guests will have no incentive to keep YOUR level of cleanliness up in their space and we, like @Jessica-and-Henry0, do not allow them to clean our linens (imagine if they got something on the sheets and just kept using them and the stain sets for weeks before you get to it - or worse, they bleed through and the mattress pad does not being cleaned - ugh!). If the guests want more than once a week, we charge an additional cleaning fee. Overall, this lends to a better room and bathroom experience for them and us. We don't ask the guests to do more than pick up after themselves in the common areas and we clean as normal.
2. We charge $2/load for washing any clothes. That includes a Tide Pod and free use of the dryer. This way we have control about how much soap, etc, goes into our machines and limits the frequency in which guests do laundry.
3. We have limit on what they can use in the kitchen and hold people accountable for cleaning up after themselves when they use that space. We set expectations about use during our conversations leading up to the beginning of the booking. Then we show them where the cleaning products are in the kitchen. We have a dishwasher so they can load their own dirties but insist on hand-washing any wine glasses so we just do those ourselves. We also unload so we can put things away and, again, inspect for damage.
4. We provide a "Pantry Package" for $1/day of use (staples like flour, sugar, spices, and condiments). You can go broke giving away odds and ends like a 1/4 of flour or use of the mayo. You probably also don't want all those duplicates left over in your home or having to find room for 2 of everything. With our package, you get 2 slices of bread and we provide eggs at $1 for 2. We had to do this after our first long-term guest because we provide breakfast and they would "take" 2 slices of bread for breakfast which turned into their lunch and the innocent, "oh, I don't have any mustard, can I use yours?". Long term guests get really familiar, like you are roommates, and unless you are priced for the "shares" that come with a roommate, then you will be buying for 3 people. The $1 isn't much, but it does set an expectation that it is still a business and things are not free for the taking - even if it is ONLY a pat of butter. Hotels know this process well - that mini-fridge and room service are expensive for a reason! Just be cautious.
5. We also provide shared meals with us by preparing a menu in advance of the week and asking if they would care to join us. Depending on the ingredients, we charge $10 - $15. It's way cheaper than eating out (unless you love McDonalds) and encourages guests to buy less and take up less space in the kitchen. We've heard horror stories of guests making elaborate meals and just making a mess of the kitchen so much so that the host cannot even make their own meal. This way, a guest can get a home-cooked meal, stay out of my way, and be offered the opportunity to interact with us socially. This may or may not be for you, but almost ALL of our guests who stay more than 10 days take us up on this at least once. This is also because we do not allow use of the stove, oven, or knives so unless they'd rather nuke a microwave dinner, this is typically a better option.
6. When the guest stays for a long while, we take the opportunity to be tour guides early on and show them around. This humanizes us and helps set a tone that we want to make their stay enjoyable. It helps open the line of communication so that problems don't fester for either of you.
Additionally, it is a bad idea for you to take all the risk by blocking your calendar for them during a "trial". Personally, I am a "bird in the hand" type of girl instead of "2 in the bush" because, without a penalty, they have no incentive to stay. Reservations can always be broken by either the host or the guest. That way you are covered. You also want to make sure that there are no laws in Montreal that will give these guests "tenant rights" so that you would need to evict them to have them removed. This has happened in some locations.
Hope my perspective provided some insight.