I frequently get asked if it's important to upgrade from a cropped sensor camera to one with a full frame sensor for shooting real estate photography.
The video to the right, by Manny Ortiz, compares a Sony A9 full frame camera to a Sony A6500 cropped sensor camera. You can see that there is essentially no difference between the full frame and the cropped sensor images.
Will you be able to the difference if you upgrade? Sometimes but your clients typically can't tell the difference. For real estate photography, a full frame camera by itself does not noticeably improve your work. It's what goes on behind the camera that improves your work - the lighting, composition, and color.
In real estate photography, the lens can be an important factor. Many interior photographers like to use a tilt-shift lens which requires a full frame sensor to retain their wide angle effective focal length. But a tilt-shift lens is not essential.
So in general, for real estate photography, keep your costs down and stick with cropped sensor gear.