I just got a call from a client that has owned a house for 25 years. He plans to sell next year and asked what he should do - leave the house has is or do some remodeling and then sell?
The answer is almost always to do some inexpensive remodeling. If the house is in the median range between $500k and $1 million, you will almost always get more money by spending some money. That's because buyers want to get paid for their time if they have to remodel a house after they buy it. They don't just add the cost of the work and subtract from the market.
But another important factor is the time it takes to sell. A home that is in good condition will usually sell faster. A home that need a lot of work may never sell at all. Listings that sell fast also usually get near full price, or in today's market, even over asking price.
My client and I discussed some inexpensive things he could do to his house. Here they are in no particular order. 
- Replace his 25 yr old carpet with bamboo flooring. It's cheap at under $1 a foot, and it's sustainable. Bamboo grows fast. For a 1500sqft house, you could install it yourself and spend very little money.
- Paint. Inside and outside can be painted for a few thousand, and can make or break a buyer's willingness to purchase.
- Replace his bathroom vanities for a few hundred dollars each. Even a cheap, off the shelf vanity for $300 can make the house seem a lot nicer. This vanity to the right is $199 at home depot.
- Replace his kitchen counters and cabinet doors with off the shelf non custom products for about $3000 total.
- Replace all the doorknobs, fixtures, switches, outlet covers, etc. 25 years ago, those things were ugly. Now you can buy them online for a few bucks each.
At this point a seller has spent well under $20k, and the house is transformed. The list price can probably go up by $50k, and the house will sell in a few days instead of a few months.
Bottom line - spend the money to make your house look nice, but don't overspend on it.