The poor are sometimes adversely impacted by gentrification. "Gentrification" by definition refers to the movement into low-income communities of higher-income families who are taking advantage of the lower-cost real estate available. Once they've moved into the lower-income neighborhood, the new residents make structural improvements, like painting, roofing, landscaping, that improve the property. When multiple families or individuals similarly move into that neighborhood, and similarly improve the value of the property, it increases the value -- and therefore increases the property taxes -- for all families in that neighborhood.
The result of those improvement, and consequent increases in property values and tax rates, is to force out the remaining lower-income families, who can no longer afford the tax rates designated for that community.
Those who benefit, therefore, from gentrification, are the new residents, who bought their property for low prices and now reap the benefit of the increased property values, and the city in which the community resides, which now takes in more in property taxes than it had when the neighborhood was full of low-income housing. Additionally, small businesses in the community now enjoy customers with higher levels of disposable income. Businesses that, like the lower-income families forced to move, can no longer afford to remain in that neighborhood because of increased leases, vacate and are replaced by businesses that cater to higher-income customers.