We buy houses that sellers decided not to renovate. That is the flipping business. So we have a very clear view of what those sellers left on the table, and of what they were right to skip.
Projects that usually return money before a sale: paint, lighting, flooring repair or refinishing, a kitchen refresh (not a gut), a primary bath refresh, and curb appeal. These are cheap relative to their effect in photos and in person.
Projects that usually don't: full gut kitchens, additions, high-end custom anything, and finishing a basement to sell. Buyers will not pay you back dollar for dollar on custom work they didn't choose.
The honest middle path is a pre-sale consultation. We walk the house, look at the comps, and tell you which projects are worth doing and which ones to leave for the next owner. Sometimes the answer is 'paint and stage it.' Sometimes it's 'sell it to an investor and skip the hassle.' Either way you decide with numbers.