All in all, it's been hugely rewarding for me. Fun stuff. :)
Ive been doing Turo far longer and with 8x as many cars as you. Your experience doesn't count for anymore than mine. So based off of your region and vehicle description, I looked up your micro fleet and they appear absolute trash heaps. It cannot inspire confidence in your customer base to settle into their grand canyon trip in a 200k mile vehicle. If I woke up in your shoes Id sell em all and use that capitol to buy one 30k, 2011 or newer car. It can be luring to by the cheapest car you can find within the age requirements and throw it up on the app, but in the long run this comes back to bite you, eventually. Just my 2 cents.
People leaving your car a mess is one thing, and sometimes its laughable compared to the situation you could find yourself in. Are you aware that any vehicle with more than 130K miles at the time of listing or a salvage title will 100% denied all insurance claims though Turo? They'll run a Carfax before they pay you a dime. I was told that because they are being sued by their insurance provider, that they are trying everything they can to NOT pay damage claims. They are trying to protect their float, at all costs. I had a whopping 63% reduction in number of claims paid out by Turo to me in 2016 (claim denial). This is money for damages that the owner of the car is liable for and left holding the bag. It gets much worse heaven forbid someone is injured though.
When someone is seriously injured/damaged by a car you are the registered owner of you will not escape litigation if Turo denies your claim, as someone must pay medical, property damages and legal fees. Turo has no long term interest in backing up owners in court (extremely unprofitable). I recommend re-reading the Turo terms of service to find out how powerless you actually are when you click the "Agree" box. There is a reason rental car companies, across the board, do not rent to under 25 year olds....Risk. Turo has zero issue with renting to anybody with a fresh license and a head.
If you are going to do this I recommend your cars are put in the name of a solid LLC, otherwise you are opening your precious 401k/Savings, fire money, err whatever you own to being judged against should the car you personally own causes loss. What Im describing is a perfect storm scenario in which there is serious loss. If in such case Turo denies the claim do to what they deem "exceeded mechanical/mileage limits", or "title status" your screwed. Once your personal insurance company becomes aware you were not the driver, but in fact renting the vehicle they will also immediately deny the claim and drop you completely. The insurance of the injured/damaged is now going to seek compensation for the damages from whatever personal wealth you have now or may earn in the future. Insurance companies are not your buddy or pals and 6 months to a years worth of legal fees and civil court appearances will drive this point home.
Turo makes it easy to sign up and doesn't even want to know the VIN of the vehicle they are supposedly insuring (no other insurance underwriter on earth cuts you a policy without verifying a VIN first), just a couple of pictures, and the address of where your car gets rented from and boom... making money in your sleep. People rarely factor in the management of risk into scenarios when they are handing over the keys of a 4,000 lbs. missile (with there name on it) to a 19 year old complete stranger. Its much easier to be blinded by dollar signs.