Rationale for expression “Fixer-upper”

Solution 1:

My first guess is that it's because the property needs to be fixed up or requires a "fixer-upper", i.e., somebody who can fix it up. Phrase Finder suggests something similar:

What we now think of as a 'fixer-upper' comes to us from the USA as a colloquial term for 'something that needs fixing up'. The first mention of this in print appears to be an advertisement for a house, in The Los Angeles Times, October 1948:

Prior to that coinage, a 'fixer-upper' was 'a person who fixes things'.

Under 'Origin', reference.com simply states:

fix up + -er , pleonastically suffixed to both words

Solution 2:

The phrase fix up means

to clean, repair, or decorate something:

They take old furniture and fix it up.

I'm going to fix up the house before my mother-in-law arrives.

The term fixer-upper refers to

A house or other dwelling that is badly in need of repair, usually for sale at a low price.

A fixer-upper is a house that needs to be fixed up.