In most cases, homeowners can sell their house as it is without any upgrades. I always recommend cleaning and some fresh paint and fixing plumbing leaks and electrical problems. If the water is old and rusty it is best to replace it before putting the house on the market.
No two houses are the same and home buyers are unique too so there isn’t any hard and fast rule as to what kind of payback, if any, there might be on a specific upgrade. In general smaller improvements tend to pay for themselves. Examples include exterior doors, a new backsplash, some new light fixtures and some new kitchen appliances.
Here are some numbers from the National Association of Realtors:
Even though it is true that the kitchen will sell the house home sellers usually spend more than they get back. It is very easy to spend too much on a new kitchen.
I encourage homeowners to look at pictures of homes in the neighborhood that have sold in the last couple of years. If the current kitchen is typical for the housing style and neighborhood it doesn’t need an upgrade to sell the house. If the kitchen is below average for the area and the housing style then an upgrade might be needed.