I've been renting lower level in my house for 5 years to visiting students, and now, since I RE and don't get many student referrals, I full time Airbnb (I guess I have started too cheap for the area on Airbnb- my first Airbnb tenant told me, so I'm booked till mid January now without breaks). I'm new to Airbnb (I allow booking without my approval), so it's a learning curve, but my first two were better than my typical student-tenant. In my arrangement, my tenants don't have an access to my quarters, and I give them privacy in theirs, but leave the right, in case of an emergency, to access their lower level without their permission (if I can't get the permission soon enough).
It's a mitigated risk, there is not much they can steal, but a few small items "walked away," like a pair of wireless earphones (I would have not even noticed, but they were on one of the pictures I post to advertise), then one time it was an iron, but they sent it back, so I guess an "accident." One of my student-tenants left me her TV for free, she didn't want to drag it with her across the country. Actually tenants leave behind many usable items; I did a "final walk-through" with my student-tenants, so they do leave those items.
I'm surprised that so many people voice their fear of strangers, when in fact most murders, rapes and such are committed by family members, friends, or someone who victims knew. Police always starts with family members and friends. In my case, the biggest mess I had to clean in my lower level was left by a tenant who I personally knew very well. I had to actually help him move out, load things into his car, patch walls that got somehow damaged (not a big deal for me), touch up some paint and spend significant time returning the place to my level of cleanliness. The second place takes a student who brought a friend and the friend brought his wife and... drum rolls ... a baby, without telling me. I knew about the friend, but the wife and the baby were a surprise. Wasn't that big of a deal overall, but since then I introduced mandatory lease signing, first, with a provision - no guests without my approval, second. Those tenants also left some mess (baby wall paintings) that required some walls touch up paint.
Otherwise, for 5 years my house only got better because of the tenants.
-I have installed Nest thermostat for the tenants (was rebated by our local electrical company, plus an annual discount). Not only it saves energy, but it also gives me a piece of mind when I'm out of town and a storm passes my area, I always know if the power in my house is out. This is also my first step to the smart house upgrade.
-I have found out that I had mice infestation (without tenants I didn't go to the lower level often enough to notice). I got two farm kittens who took care of the problem and now keep the whole neighborhood in shape; my neighbors told me that their flowers that were not blooming for years, are finally blooming again - our rabbit population got under control.
-I got a clone for my Internet (tenants complained enough that some places in the house are dead). Now, with the clone, the Internet got stabilized throughout. $50 investment, and everyone's Internet improved tremendously. The clone is on the opposite to the router side of the house and now I can get a desktop for my son that he can plug into the clone directly to have a wired connection. Before the clone there was barely any wireless connection and it seemed pointless to buy him a desktop.
-Tenants also complained about my loud sprinkler system, which bugged me too, but without the tenants I wouldn't have been on to "solving the problem" so much. I finally figured that I needed to replace my water meter and while doing that also installed a pressure reducing valve (now standard in any new builds). And that solved the problem of phantom toilet flashing and leaking faucets throughout the house, in addition to very quiet sprinkles.
-Plus, there is less of a chance when I'm out of town, that someone would break in, since my tenant's car is in the driveway.
In short I'm left (politically speaking), but I do NOT trust people. I do a thorough google check of all my tenants, but to be fair it's a very poor predictor of messiness, or how clumsy they are, or if they are going to use a white towel as a floor mat, or wash it with their dark clothes. My fault, no more white towels, dark grey it is. I can write a book about all my tenants, weird things they did, or left. But those are mostly amusing stories, nothing that would make me stop renting. And the person who I knew very well, who left a huge mess, in life is very clean (more than me even), but in my place was a total mess (maybe he was depressed, who knows, overwhelmed).