Gentrification is the process of increasing affluence in a neighborhood. It leads to higher property values and higher rent rates. It is generally considered to be good for property owners and bad for tenants. Often groups with conflicting interests will actively try to promote or combat gentrification.
The city tried to promote gentrification through the Renaissance Pointe project by building $120K homes on the southeast side. Opposition from neighbors was to be expected, since it could have lead to an increase in rent. But the real reason it didn't work is because people aren't going to spend six figures to live between Creighton and Pontiac. People generally prefer to have neighbors with the same socioeconomic status.
Gentrification has to start with affordable housing. First-time home buyers look for quality bargains. After a few homeowners establish themselves, the respectability of the neighborhood improves and house prices go up.