Car or not? In about 30 sits, I’ve rented once, driven my own car to the sit about 10 times, used public transportation maybe 10 times and used the HO’s car about 10 times.
For my 3 international sits, the HOs’ offered the car - one in Somerset was out in the country and there was no reasonable bus to even get groceries, in Edinburgh I was set up to use the car but never did, and on Jeju Island you really needed a car as the home was in a ‘country’ subdivision.
Here in the US I’ve done sits w/o a car - Portland, OR, Denver, CO and Brooklyn, NY for example. Other sits really weren’t reasonable w/o a car - a Los Angeles suburb.
Here in the US in many cities we have local short term rental but I’m not sure whether you need a US license and the same for international companies.
In the US, there is a car rental company called Turo.com that allows people to rent their own cars. Lots of fancy luxury cars on the site but also cars for $15 to $20 a day for an older smaller car.