The biggest single error amature photographers make, I think, when taking indoor pictures for their listings on selling venues or websites is to use the wrong lighting. You can't get good lighting with just the camera flash and you don't want to mix lighting types like incandescent bulbs, the camera flash, and natural lighting from a window. The results can be poor image sharpness and poor color rendering.
But there is an easy, affordable solution. You don't need expensive photo lights and reflecters. One of the cheapest, and best, general purpose photo lights is a full-spectrum (5000K to 5900K) fluorescent light. These are available is several formats but the screw-in incandescent-replacement "twisty" bulb or the standard four-foot tube style are the most common and the easiest to use. For the "twisty" type you can use those small clamp-on sockets with the aluminum or steel reflectors. For the four-foot tubes a double mount shop light will suffice. You can get either of these and the bulbs at most hardware stores or home fixture stores. Sometimes you may have to order the bulbs as the may not be a high volume item for smaller stores.