In addition to your required annual inspection you will also be required to complete a 100-hour inspection every 100-hours of operation.
You will need a commercial insurance policy which allows you to rent the aircraft.
This policy covers the aircraft, so you will also need (or at least want) general liability insurance and all the other trimmings that come with operating a business.
This is a broad category. There's no way we can cover it all. You will however need to consider:
Maintaining an adequate stock of "service spares" to maintain the aircraft.
Tires, light bulbs, oil, oil filters, 5606 hydraulic fluid, etc. - As an individual owner you may be OK with being down for a week waiting for parts, but as a rental operation that will lose you customers.
Having a relationship with a mechanic to do the maintenance
Owner-Performed Preventive Maintenance goes out the window when the aircraft becomes a rental - you may still be able to assist your mechanic, but you can no longer do & sign-off on things like oil changes.
Vetting your renters
Rental aircraft at an FBO/Flight School live a hard life. If you like your plane and want it to stay in good condition you'll need to vet your renters a bit more thoroughly than "You have a pilot's license and you went around the pattern without hitting anything" - Find the kind of pilots who will police their trash from the cabin, lean the mixture appropriately, etc.
The top rated answer is incorrect. If the aircraft is to be rented out to licensed pilots (i.e. not for instruction, but rather straight rental, just like renting a car) then the 100 hour inspections are not required.
The top answer is not correct. If you’re purely renting the aircraft out, it DOES NOT need a 100-hr inspection.
The 100-hour inspections are defined under FAR 91.409:
The 100-hour inspection is required for aircraft:
That carry any person (other than a crew member) for hire; or
That are provided by any person giving flight instruction for hire.
The phrase "for hire" refers to the PERSON, not the aircraft. The common FBO rental aircraft scenario always comes up. Ya, you're paying to rent the aircraft, but you're not hiring someone to fly it. Rental aircraft don't require a 100-hr.
Any operation that supplies both the flight instructor and the aircraft, requires a 100-hr. This is in contrast to a student pilot who provides their own aircraft and hires an instructor -- a 100-hr is not needed. This also falls in line with general commercial activities. Flight schools will routinely get to the 98ish hour mark, cease flight instruction in that plane and then allow it to just be rented until they can get it scheduled for their 100-hr. Happens all the time.