Hey man, I understand the confusion and would like to correct some notions. Particularly with some comments here conflating socialism with other ideas.

Socialism is simply workers controlling industry. This may mean many things including each business being controlled by it's individual workers, all industry being collectively owned by society as a whole, or other similar ideas. Personally I believe in the former. As long as the people working in a business control said business this is socialism

What if that industry is the rental of tractors? Well, then all workers involved in this business must control the business. If you are the sole worker, the only one operating this business, then you have sole control.

If you were to, let's say, buy 10 tractors and bring on a receptionist to manage calls and schedule tractor usage well then that receptionist would also own, and control, this business as well. Same goes as it grows. Just as a person selling wheat to a grain mill doesn't need to hold any ownership over the grain mill nor the mill over the farm you selling your tractors usage doesn't need those using it to own your tracker.

Socialism does not necessitate the collective ownership of property nor does it mean industrial rental isn't an option. It only necessitates that the workers control industry. This may mean that each individual business operates as it's own entity, controlled by it's individual workers.

Workers seizing the means of production can mean does not mean, necessarily, society owning it collectively nor does It mean all who use it may have ownership.

I feel that socialism and communism often get conflated. Private ownership of property and the means of production is allowed under socialism, just not ownership over industry. You can personally own and rent out a tractor but you cannot personally own a tractor rental company. Under communism, all is owned collectively

Now, the morals of renting are another thing altogether and entirely detached from socialism. Personally, I think it mostly immoral. Under your circumstance I see no issue selling excess time with a tool you use for the majority of the time. The issue comes when a single renter start to pay entirely for maintenance with excess profits. In my opinion, this should grant them partial ownership. Once more though this is detached from socialism entirely